Load-resonant converter with zero current switching and variableoutput power

The authors present a half-bridge series-parallel load-resonant converter in which the resonant circuit has been designed so that the circuit can operate near to resonance over a wide frequency range. The output power of the circuit varies continuously over this frequency range, resulting in a load-resonant converter with zero current soft-switching over a range of output power. The prototype constructed shows a power variation of 2:1 over a frequency range of 30 kHz     

Simple constant frequency constant current load-resonant powersupply under variable load conditions

A power supply incorporating a load-resonant converter operating at a fixed frequency and capable of efficient operation with a constant current characteristic, independent of the load conditions, is presented. The simple resonant circuit is designed so that at one of its multiple resonant frequencies both the load current and the resonant frequency are independent of the value of the load. A power supply is designed and constructed which delivers over 1 kW to a variable load at a constant switching frequency of 82 kHz     

Phase-controlled series-parallel resonant converter

A constant-frequency, phase-controlled, series-parallel resonant DC-DC converter is introduced, analyzed in the frequency domain, and experimentally verified. To obtain the DC-DC converter, two identical series-parallel resonant inverters are paralleled and the resulting phase-controlled resonant inverter is loaded by a voltage-driven rectifier. The converter can regulate the output voltage at a constant switching frequency in the range of load resistance from full-load resistance to infinity while maintaining good part-load efficiency. The efficiency of the converter is almost independent of the input voltage. For switching frequencies slightly above the resonant frequency, power switches are always inductively loaded, which is very advantageous if MOSFETs are used as switches. Experimentally results are given for a converter with a center-tapped rectifier at an output power of 52 W and a switching frequency of 127 kHz. The measured current imbalance between the two inverters was as low as 1.2:1     

大功率ESP高频高压电源

针对静电除尘用工频电源存在缺陷,设计了一种静电除尘用高频开关电源,分析了各开关模态,采用基波近似法对LCC谐振变换器进行了分析,并用saber软件进行了仿真验证.仿真结果表明,控制频率与输出电压之间的关系具有非线性特点,越接近谐振频率,这种非线性越明显;电路开始谐振的阶段,谐振电路有明显的电流冲击,这可能会对主回路中的器件特别是IGBT产生较大电流应力.     

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     

Design of a 1-MHz LLC Resonant Converter Based on a DSP-Driven SOI Half-Bridge Power MOS Module

In this paper, the design of a 1-MHz LLC resonant converter prototype is presented. Aiming to provide an integrated solution of the resonant converter, a half-bridge (HB) power metal oxide semiconductor (MOS) module employing silicon-on-insulator technology has been designed. Such a technology, which is suitable for high-voltage and high-frequency applications, allows enabling HB power MOSFET modules operating up to 3MHz with a rated voltage of 400V. The power device integrates the driving stages of the high-side and low-side switch along with a latch circuit used to implement over-voltage/over-current protection. The module has been designed to be driven by a digital signal processor device, which has been adopted to perform frequency modulation of the resonant converter. By this way, output voltage regulation against variations from light- to full-loaded conditions has been achieved. The issues related to the transformer design of the LLC resonant converter are discussed, too. Owing to the high switching frequency experienced by the converter, 3F4 ferrite cores have been selected for their low magnetic power losses between 0.5 and 3 MHz and core temperatures up to 120degC. The resonant converter has been designed to operate in an input voltage range of 300-400V with an output voltage of 12V and a maximum output power of 120W. Within these design specifications, a performance analysis of the LLC converter has been conducted, comparing the results obtained at the switching frequencies of 500kHz and 1MHz. A suitable model of the LLC resonant converter has been developed to aid the prototype design.     

Analysis and design of an LCL-T resonant converter as a constant-current power supply

An LCL-T resonant converter (LCL-T RC) is shown to behave as a current source when operated at resonant frequency. A detailed analysis of the LCL-T RC for this property is presented. Closed-form expressions for converter gain, component stresses, and the condition for converter design optimized for minimum size of resonant network is derived. A design procedure is illustrated with a prototype 200-W 20-A current-source power supply and experimental results are presented. The LCL-T RC as a current source offers many advantages such as easy parallel operation and low circulating currents at light load. Additionally, with appropriate phase shift in paralleled modules, the peak-peak ripple in output current is reduced and the ripple frequency is increased, reducing filtering requirements. The leakage inductance of a transformer can be advantageously integrated into the resonant network. These merits make the topology applicable in various applications such as magnet power supply, capacitor charging power supply, laser diode drivers, etc.     

A Radar Power Supply Without A Voltage Droop

A new principle of fine regulation applied on a high-voltage line supplying a pulsed load (radar tube) is presented. The high-voltage power-supply system is a combination of a single-series resonant converter and an efficient capacitor multiplier in the output stages. The electronic power-conversion system uses a Schwarz converter employing a series resonant circuit for the transfer and control of power. An internal frequency of 35 kHz enhances the power density of the converter model. This model provides 16 kV for the helix-cathode circuit of a klystron with an accuracy of 0.50/00 (per mille) and 11 kV for the collector-cathode circuit with an accuracy of 5 percent. The presentation is supported by experimentally acquired data. The improved high-voltage power supply should lessen the problems associated with high-voltage transformers and the high accuracy required for the voltage control for the helix-cathode circuit to avoid distortion in the returning signal of a space-borne radar system.     

Electromagnetic considerations in power electronic converters

Electromagnetic effects have an important influence on all aspects of power electronic design. The effects of stray magnetic and electric fields on circuit performance, and the necessity to control the resulting stray inductance and capacitance by good circuit design practices are introduced. Inductors are key components and the pressure to design to meet high-frequency specifications is relentless. Four types of inductors are discussed briefly and their electromagnetic properties are compared and contrasted. High-frequency transformers are discussed in terms of their impact on circuit behavior and their major design issues. The limitations of conventional topologies at multimegahertz frequencies are explored. A circuit example of a half-bridge series-parallel resonant converter working between 1-2 MHz and implemented using hybrid technologies is used to demonstrate how circuit, component and layout design are electromagnetically interdependent     

TRIAC dimmable ballast with power equalization

A two-stage, two-wire TRIAC dimmable electronic ballast for fluorescent lamps is presented in this paper. It is constructed by using a flyback converter as the input power factor corrector to supply a half-bridge series-resonant parallel-loaded inverter to ballast the lamp. The flyback converter is operated in discontinuous conduction mode so that the filtered input current profile is the same as the TRIAC-controlled voltage waveform. The switches in the inverter are switched at a constant frequency slightly higher than the resonant frequency of the resonant tank. Based on the constant average input current characteristics of the inverter, the dimming operation is simply achieved by pulsewidth modulation control of the magnitude of the flyback converter output voltage. No synchronization network is required between the input and output stages. In addition, a linear power equalization scheme is developed so that the dc-link voltage (and hence the lamp power) is in a linear relationship with the firing angle of the TRIAC. The average output voltage of the dimmer controls the equalized flyback converter output voltage. Modeling, analysis, and design of the ballast will be described. A prototype was implemented to verify the experimental measurements with the theoretical predictions.     

Efficient resonant power conversion

The DC analysis of a series-resonant converter operating above resonant frequency is presented. The results are used to analyze the current form factor and its effect on the efficiency. The selection of the switching frequency to maximize the efficiency is considered. The derived expressions are generalized and can be applied to calculations in any of the switching modes for a series-resonant circuit. For switching frequencies higher than the resonant frequency, an area of more efficient operation is indicated which will aid in the design of this class of converters and power supplies. It is pointed out that (especially for power MOSFETs where ohmic losses dominate) it is more attractive to select switching frequencies that are higher than the resonant frequency because of the possibility of nondissipative snubbers. Slowing down the rise of the gate voltage and, hence, the slow decrease of ON resistance during turn-on is also not a drawback to high-frequency switching. Because of this safer operation, the standard intrinsic diode of the power MOSFET could be used at high frequencies instead of the more expensive FREDFET     

A high-performance ZVS full-bridge DC-DC 0-50-V/0-10-A power supplywith phase-shift control

This paper presents a high-performance DC-DC switching mode power supply designed to deliver a regulated 0-50 V/0-10 A output. The proposed power supply is based on a modified version of the zero-voltage switching (ZVS) full-bridge (FB) phase-shift DC-DC converter, which incorporates commutation auxiliary inductors to provide ZVS for the entire load range as well as a commutation aid circuit to clamp the output diode voltage. The control strategy is based on two control loops operating in cascade mode. The inner loop maintains a regulated output current, whereas the external voltage loop regulates the output voltage, independently of load and input-voltage changes. In order to obtain a high-reliability converter, the control circuit has been implemented using just two integrated circuits (ICs). The phase-shift regulator UC3875 IC generates the gate drive signal to the MOSFET's. The control loop regulators are implemented using the TL074 IC. A theoretical analysis was conducted, and experimental results were obtained for a 0-50 V/0-10 A power supply operating at 100 kHz     

An Analysis of the ZVS Two-Inductor Boost Converter under Variable Frequency Operation

The two-inductor boost converter has been previously presented in a zero-voltage switching (ZVS) form where the transformer leakage inductance and the MOSFET output capacitance can be utilized as part of the resonant elements. In many applications, such as maximum power point tracking (MPPT) in grid interactive photovoltaic systems, the resonant two-inductor boost converter is required to operate with variable input output voltage ratios. This paper studies the variable frequency operation of the ZVS two-inductor boost converter to secure an adjustable output voltage range while maintaining the resonant switching transitions. The design method of the resonant converter is thoroughly investigated and explicit control functions relating the circuit timing factors and the voltage gain for a 200-W converter are established. The converter has an input voltage of 20V and is able to produce a variable output voltage from 169V to 340V while retaining ZVS with a frequency variation of 1MHz to 407kHz. Five sets of theoretical, simulation and experimental waveforms are provided for the selected operating points over the variable load range at the end of the paper and they agree reasonably well. The converter has achieved part load efficiencies above 92% and an efficiency of 89.6% at the maximum power of 200W     

一种反激式LED恒流驱动电路的设计与实现

设计了一种输出功率达120W的反激式变换LED恒流驱动电路,其输出电压范围为33～37V,可为120只功率为1W的LED管采用10串12并混联方式组成的LED阵列提供驱动电流。对其功率因数校正电路、反激式变换电路、恒流控制电路进行了设计和试制,性能测试表明,其输出恒流效果较好,电流稳定度约2.7%,输出电压纹波低,可用于恒流驱动混联方式组成的多只LED阵列。     

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.     

Analysis, design and experimental results of a high-frequency power supply for spark erosion

The LC/sub s/C/sub p/ resonant converter finds a new application in an electrical discharge machining (EDM) power supply, which is designed for the purpose of developing small size EDM systems. The switching frequency is tuned to the natural resonant frequency where the converter tends to act as a current source. In this way, three effects are achieved: 1) the necessary over-voltage is generated, first to ionize the dielectric and then to establish the electric discharge, 2) a constant current is supplied during the machining of the workpiece, providing the circuit with inherent protection under short circuit conditions, and 3) overall stability is guaranteed despite the equivalent negative resistance of the dielectric breakdown. The proposed control achieves an optimum and stable operation using tap water as dielectric fluid preventing the generation of undesired impulses and keeping the distance between the electrode and the workpiece within the optimum stable range. The EDM power supply has been validated to perform operations in a nuclear power plant application.     

Self-sustained oscillating resonant converters operating above theresonant frequency

This paper presents a new control technique for resonant converters. Unlike conventional variable frequency control which externally imposes the switching frequency, the proposed scheme is based on controlling the displacement angle between one of the resonant circuit variables, typically the current through the resonant inductor, and the voltage at the output of the inverter. As a result, zero-voltage switching (ZVS) can be ensured over a wide operating range. The proposed control technique cam be applied for series, parallel, and series-parallel resonant converters. As an example, the static characteristics and dynamic model of a series-parallel resonant converter with the proposed controller are derived and the system behaviour is investigated in detail. Experimental results are given to demonstrate the operation of resonant converters with the proposed controller and to validate the analysis     

High power laser diode driver based on power converter technology

This paper describes the design of a high speed semiconductor laser diode driver designed for driving 500 mW to 1.5 W diodes at full optical power modulation up to frequencies of 10 MHz. The duty cycle of the modulation may be varied. A switching power-converter based current source allows a higher power delivery efficiency to the diode than in previous designs, allowing for a more modest power supply and dissipation requirements. A dynamic ripple cancellation circuit reduces the power converter output current ripple to less than 1% of full-scale current. The circuit is capable of delivering up to 2.5 A to a laser load, with a 10-90% switching risetime from laser threshold to full on of less than 20 ns     

A high efficiency charge pump circuit for low power applications

A high efficiency charge pump circuit is designed and realized. The charge transfer switch is biased by the additional capacitor and transistor to eliminate the influence of the threshold voltage. Moreover, the bulk of the switch transistor is dynamically biased so that the threshold voltage gets lower when it is turned on during charge transfer and gets higher when it is turned off. As a result, the efficiency of the charge pump circuit can be improved. A test chip has been implemented in a 0.18 μm 3.3 V standard CMOS process. The measured output voltage of the eight-pumping-stage charge pump is 9.8 V with each pumping capacitor of 0.5 pF at an output current of 0.18 μA, when the clock frequency is 780 kHz and the supply voltage is 2 V. The charge pump and the clock driver consume a total current of 2.9 μA from the power supply. This circuit is suitable for low power applications.     

高功率CO2激光器谐振开关变换型电源的计算仿真

研究了高功率CO2激光器用零电流开关准谐振开关电源,讨论了电源的工作原理和电路结构,进行了激光电源的计算仿真研究,得到了谐振电路的工作波形,通过谐振开关方式与PWM硬开关方式的比较,论述了零电流开关准谐振变换器的技术特点及优势。