Four-junction AlGaAs/GaAs laser power converter

Four-junction A1GaAs/GaAs laser power converters (LPCs) with n+-GaAs/p+-Al0.37Ga0.63As heterostructure tunnel junctions (TJs) have been designed and grown by metal-organic chemical vapor deposition (MOCVD) for converting the power of 808 nm lasers.A maximum conversion efficiency ηc of 56.9％ + 4％ is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W,while dropping to 43.3％ at 1.5 W.Measured current-voltage (I-V) characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC.     

Monolithic GaAlAs/GaAs infrared-to-visible wavelength converter with optical power amplification

A monolithic wavelength converter has been constructed in the GaAlAs alloy system which comprises a wide gap emitter phototransistor and a double heterojunction (DH) light emitting diode (LED) in a bifacial configuration. The liquid phase epitaxy (LPE)-grown structure is capable of efficiently converting IR light with λ < 870 nm into the red spectral range in conjunction with optical power amplification.     

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     

Coupling of power from a circular confocal laser with an output aperture

An iteration technique is used for a theoretical study of the field distributions and diffraction losses at the reflectors of an asymmetric confocal cylindrical resonator having an output hole in one mirror for the low-loss TEM00and TEM10modes with Fresnel numbers ofN = 0.8and 1.2. A digital computer is used to numerically iterate an initially launched uniform distribution as it reflects back and forth between the mirrors until a steady-state field distribution occurs. The edge and coupling hole diffraction losses and the power coupled from an output hole in one mirror are also computed. The presence of the coupling hole produces a perturbation of the field distribution with distortion of the field increasing for increasing Fresnel number and for low-order modes. The relationship between hole radius and power output is presented. An optimum-size coupling hole may be selected from this data, which will yield maximum power output in the mode of operation desired. It has been found that, with the use of a coupling hole, mode selection of the lowest order TEM00mode is possible for resonators having large Fresnel numbers (N > 1.0).     

一种基于CUK变换器的通用型固体激光电源

介绍了一种性能优异的新型固体激光电源。采用新型的变换器结构,使电源具有较强的通用性。给出了原理电路模型,分析了工作原理。实验证明,该电源结构简单、适应范围广、成本较为低廉、工作可靠。     

不同空间分布光束通过聚焦光学系统传输特性的比较

基于柯林斯公式和ABCD传输矩阵理论，在相同激光功率和初始束宽下，研究了不同空间分布光束通过聚焦光学系统的传输特性，结果表明，入口处不同阶次的超高斯光束在距离光学系统焦点一半的位置（z=f/2)，光强分布的差别很大，轴上光强随着阶次的增加，先增加，然后减小至固定值；聚焦光学系统入口处超高斯光束的阶次越大，即光强分布越均匀，在光学系统的焦点位置（z=f)，光轴上激光强度越大，直至趋于固定值，但光强分布的差别不大。     

A bidirectional AC-DC power converter with power factor correction

This paper presents new operation and performance of a thyristor-based AC-DC current-controlled boost-type converter that allows bidirectional power handling capability and provides input power factor correction and a near-sinusoidal input current waveform. The new converter can reduce harmonic pollution and disturbance on the supply mains. The feature of bidirectional power flow allows the stored energy in loads, such as motors, to regenerate back to the supply source, leading to an increase in overall energy efficiency and possibly a reduction in the size of the DC link capacitor. The operation is confirmed with the successful implementation of an experimental prototype     

高功率CO2激光器的砷化镓窗口

本文研究一种减反膜的理论设计和实验制备技术,获得了适用于高功率CO2激光器,而且结构简单,制备方便的光学器件。     

混沌开关电源输出端有源滤波器的设计

混沌扩频技术是从源头上改善高频开关电源EMC特性的一种有效方法,但同时开关电源输出电压的纹波会随频率调制系数的增大而有所增加.为使输出电压的纹波降低到原来的水准,本文在开关电源的输出端增加一个简单的有源滤波器.这个有源滤波器结构简单、成本低、体积小、对开关电源输出电压的动态特性影响不大.本文主要阐述这个有源滤波器的设计.     

GaAs converters for high power densities of laser illumination

Photovoltaic power converters can be used to generate electricity directly from laser light. In this paper we report the development of GaAs PV power converters with improved conversion efficiency at high power densities. The incorporation of a lateral conduction layer (LCL) on top of the window layer resulted in a considerable gain in efficiency at high illumination levels. Additional performance improvements were obtained by using a metal electrode grid design and antireflection coating optimised for monochromatic and inhomogeneous laser light. Maximum monochromatic (810 nm) optical‐to‐electrical conversion efficiency of 54·9% at 36·5 W/cm² has been achieved. The characteristics of laser power converters with p/n and n/p polarity are discussed in this paper. Moreover, different materials and doping levels were applied in the LCL. The performance of these different device structures at high laser intensity is presented and discussed. It is shown that the lateral series resistance of the cell has a major impact on the overall device performance. Copyright © 2008 John Wiley & Sons, Ltd.     

A self-driven active clamp forward converter using the auxiliary winding of the power transformer

This study proposes a new self-driven active clamp forward converter eliminating the extra drive circuit for the active clamp switch. The converter used the auxiliary winding of the power transformer to drive the active clamp switch and a simple RC circuit to get the dead time between the two switches. The operation principle was presented and experimental results were used to verify theoretical predictions. A 100-W (5 V/20 A) prototype converter that only exhibited 1.5-turn winding number in the auxiliary winding was sufficient to drive the active clamp switch on the input of 50 V. Finally, the measured efficiency of the converter was presented and the maximum efficiency of 91% was obtained.     

A single-switch AC-DC converter with power factor correction

A new single-stage, single-switch power factor correction converter with output electrical isolation is proposed in this paper. The topology of this converter is derived by combining a boost circuit and a forward circuit in one power stage. To improve the performance of the AC-DC converter (i.e., good power factor correction, low total harmonic distortion (THD) and low DC bus voltage), two bulk storage capacitors are adopted. Its excellent line regulation capability makes the converter suitable for universal input application. Due to its simplified power stage and control circuit, this converter presents a better efficiency, lower cost and higher reliability. Detailed steady state analysis and design procedure are presented. To verify the performance of the proposed converter, a design example along with P-simulation program with integrated circuit emphasis (PSPICE) simulation and experimental implementation are given. The measured power factor and efficiency are 99% and 87% at low line (i.e. 110 VAC) operation, and 95% and 81% at high line (i.e. 220 VAC) operation, respectively     

4A5--Radiation interactions between laser oscillators with different active elements and different frequency

This paper presents a novel problem in laser dynamics, where two lasers using different active material with different frequency produce radiation interaction. In the first experiment, we performed a study on the effect of radiation coupling of the giant pulse ruby laser on the Nd³⁺-glass laser under normal oscillation. It was found that the sudden enchancement followed by the quenching of oscillation in the Nd³⁺-glass makes a short, intense pulse, which was one order of magnitude or more larger than usual oscillating spikes, after the excitation by theQ-switched ruby laser light. In order to explain this result, the fluorescence study of the Nd³⁺-glass in the range of the visible and near infrared spectrum was arranged by employing the giant pulse ruby laser as an exciting source. This measurement has led to valuable information on the energy levels of the Nd³⁺-ion in the glass host through the new observation of fluorescence lines in the visible spectral region. Hence it was found that the ruby laser radiation is properly responsible for two upward transitions from the ground state in the Nd³⁺-glass, and thereby such radiation coupling yields the sudden enhanced emission in the laser output.     

A DSP-based active disturbance rejection control design for a 1-kW H-bridge DC-DC power converter

This paper presents the design and implementation of an advanced digital controller for a 1-kW H-bridge dc-dc power converter. A new control algorithm based on the active disturbance rejection concept is developed to cope with the highly nonlinear dynamics of the converter and the disturbances. An experimental digital control system is used to implement the new control strategy. It consists of a digital control board based on the TMS320C6711 digital signal processor chip, an analogy I/O board, and a complex programmable logic device pulsewidth-modulation generation board. Using a newly developed bandwidth-parametrization technique, an autotuning method based on noise quantification is also developed and tested. Experimental results show the advantages and flexibilities of the new control method for the H-bridge dc-dc power converter.     

A compact DC-to-DC power converter for distributed power processing

The authors present a compact (55-W/in³), efficient (86% power train), 1-MHz switch-mode, DC-to-DC power converter contained in a 2-in by 2-in by 0.25-in, 1-in³ package. They describe the interleaved forward topology, steady-state analysis, switch transitions, capacitor substrate, planar printed-wiring-board transformer, packaging, electrical performance, power loss analysis, thermal analysis, reliability, and efficiency and power density improvements     

Linearised InGaP/GaAs HBT MMIC power amplifier with active biascircuit for W-CDMA application

A high linearity InGaP/GaAs heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) power amplifier is demonstrated using a new structure for a bias circuit for wideband-code division multiple access (W-CDMA) application. A one shunt capacitor is added to a novel active bias circuit and acts as a lineariser improving input P_{1 dB} of 16 dB and phase distortion of 5.1° for the hybrid phase shift keying (HPSK) modulated signal at the 28 dBm output power; the lineariser showing no significant increase of signal loss and chip area. The two-stage HBT MMIC amplifier exhibits a power-added efficiency (PAE) of 37%, a linear power gain of 24.5 dB, and an output power of 28 dBm with an adjacent channel power ratio (ACPR) of -45 dBc, under a 3 V operation voltage     

Voltage-source active power filter based on multilevel converter and ultracapacitor DC link

A new topology for active power filters (APF) using an 81-level converter is analyzed. Each phase of the converter is composed of four three-state converters, all of them connected to the same capacitor dc link voltage and their output connected in series through output transformers. The main advantages of this kind of converter are the negligible harmonic distortion obtained and the very low switching frequency operation. The single-phase equivalent circuit is analyzed and their governing equations derived. The dc link voltage control, based on manipulating the converter's voltage phase, is analyzed together with the circuit's characteristics that determine the capability to draw or deliver active and reactive current. Simulation results for this application are compared with conventional pulsewidth-modulated (PWM) converters, showing that this filter can compensate load current harmonics, keeping better-quality sinusoidal currents from the source. The simulated configuration uses a 1-F ultracapacitor in the dc link, making it possible to store energy and deliver it during short voltage dips. This is achieved by applying a modulation control to maintain a stable ac voltage during dc voltage drops. A prototype of the filter was implemented and tested, and the obtained current waveforms showed to be as good as expected.     

铜蒸气泵浦染料激光器输出功率与谐振腔结构的关系

一、引言 铜蒸气泵浦染料可调谐激光器具有重复率高、输出功率高等优点,是应用激光光谱中的重要激光器件。器件结构见图1。用Littrow光栅和平面镜组成了谐振腔。如图1的染料激光器的前腔板一般都采用平板玻璃(R=8％),其优点是装调方便,但考虑到染料槽的宽度只有0.3mm,光束的衍射角大(约2.5mard),因此谐振腔的衍射损耗大。在某些实际应用中,M_1与染料槽间往往还要留出一段距离以便插入光学元件,衍射损耗则将加大。为了提高器件的效率,我们采用凹面反射镜代替平板。