【作者】 左壮；

【导师】 徐殿国；

【作者基本信息】 哈尔滨工业大学 ， 电力电子与电力传动， 2008， 博士

【摘要】 随着绿色照明工程的实施,气体放电灯被广泛地使用在室内照明、户外泛光照明、汽车照明等应用场合中。但是,与之配套工作的传统电感式镇流器由于重量大、体积大、功率因数低、工频闪烁、输出功率随着电网变化、控制功能单一等缺点,已不能满足绿色照明的要求。电子镇流器作为一种照明节能电器,是实现绿色照明的关键所在。本文以小功率金卤灯数字化电子镇流器为研究课题,对金卤灯的基本特性、拓扑结构,控制策略和启动技术等问题进行了研究,在此基础上提出了一些新方法及思路,并通过理论分析和实验加以验证。本文通过对逆变电路的改进,成功的将并联谐振电路和半桥双Buck电路结合起来,设计了一种结合谐振启动方式的新型两级式数字化低频方波电子镇流器。点火阶段逆变电路工作于并联谐振模式,以谐振启动方式代替传统的脉冲启动方式,去掉了点火变压器,简化了电路结构。在稳态阶段逆变器工作于半桥双Buck电路模式,灯电压电流为低频方波,有效地避免了声共振现象,本文阐明了其工作原理并给出了参数设计方法。另外针对谐振启动方式在实际应用遇到的谐振参数离散性问题和电感易饱和问题,本文提出一种连续冲击自适应软启动控制策略,取得了较好的效果。影响功率密度的主要因素是占系统绝大部分体积的无源器件,提高功率密度的最有效的方法是尽可能提高开关频率。但当开关频率提高到100kHz以上时,工作于CCM模式的半桥双Buck变换器将不再适用,主要原因是二极管反向恢复会带来较大的损耗,同时也使得EMI问题难以解决,另外电路工作在硬开关状态,开通损耗较大。为克服这些困难,本文提出了一种基于准方波谐振的自适应零电压开通双Buck功率变换器,详细分析其工作原理,推导出了精确的输出电压增益公式及软开关条件,并给出电路参数的设计方法。自适应零电压控制策略的采用保证了在整个点灯过程中以及点不同厂家灯泡时的零电压开通。照明专用单片机AT90PWM2的使用提高了控制性能,保证了高频工作下的PWM分辨率,简化了硬件设计。70W数字化金卤灯电子镇流器样机验证了所提拓扑结构及控制方法的正确性,稳态工作频率达到100kHz以上,整机效率可达92%。金属卤化物灯因其自身特性,它的启动过程比较复杂。本文根据金卤灯启动过程各阶段及稳态的特点给出了对应的控制方法,并提出了一种单周电流峰值控制策略,有效地抑制Run-up过渡过程中及低频换向时的电流过冲问题。自适应零电压开通控制方法和单周电流峰值控制策略贯穿于各个阶段的控制策略中。自适应零电压开通控制方法除了保证开关管零电压开通之外还可满足点火暂态过程实时性的要求。基于调节导通时间的逆变器输入平均功率控制方法简单有效,通过配接各种灯泡的实验证明了该功率闭环控制策略的可行性与准确性。谐振启动方式电路结构简单控制灵活,但也有回路电流峰值高的缺点,并且其对于例如单功率级等多数低频方波拓扑结构而言,谐振启动方式将不再适用。在实际应用中,低频方波电子镇流器通常都采用脉冲启动方式,因此有必要对其进行研究。本文介绍了电子镇流器脉冲启动电路的设计要求,并提出了一种基于双频触发的金卤灯脉冲启动电路,通过对电路模型进行计算细致分析了影响点火脉冲电压幅值和脉宽的各个参量。通过添加辅助电感的方式限制了回路电流峰值并克服变压器寄生电容离散性所引起的脉冲电压峰值波动,同时利用辅助电感和变压器寄生电容组成另一谐振回路与主谐振回路共同作用,产生两组不同频率的点火脉冲序列同时加到灯端。该双频触发脉冲电压既可以提供足够大的脉冲峰值电压,又可以保证足够的脉冲宽度,有效提高点火可靠性。更多还原

【Abstract】 With the implementation of green lighting project, gas discharge lamps have been widely used in many applications including: home lighting, outdoor lighting and automotive lighting. However, traditional electromagnetic ballast cannot satisfy the demand of modern lighting system, due to drawback including large size, heavy weight, low power factor, flicker, poor power regulation and sensitive to line-voltage dips. As the new efficient lighting electrical appliance, electronic ballast is the critical issue in the green lighting project.Digital electronic ballast for low power metal halide lamp is selected as the research subject of this dissertation and several problems such as basic lamp characteristic, topology, control method and ignition technology are addressed. Some novel methods and ideas are proposed based on analysis and experiment. The main contents and achievements are listed below.Combining the Half-bridge dual Buck topology with parallel-loaded resonant (PLR) circuit, a novel two-stage low-frequency-square-wave (LFSW) digtal electronic ballast with resonant ignition is proposed. Inverter operates in the mode of PLR duiring ignition stage and external ignitor is removed. Inverter operates in mode of Half-bridge dual Buck converter in steady state. Lamp voltage and current are low-frequency-square-wave. Lamp arc is stable without acoustic resonance. Operating principle and parameter design method are represented. To solve the problem of resonant parameter tolerance and inductor saturation, an adaptive iterating ignition soft start-up control strategy is proposed and the effect is satisfied.The key factor affecting the power desity is the passive elements. The most effective way of enhancing the power desity is to increase the operating frequency. However, the Buck converter operating in CCM mode is not applicable when operating frequency is beyond 100 kHz because of the reverse recovery of diode and EMI problem. Meanwhile, the MOSFET is in hard switch mode and the turn-on loss is significant. To solve these problems, an adaptive ZVS dual Buck quasi-square-wave (QSW) dual Buck converter is proposed. The principle of QSW is explained in detail. Accurate voltage gain transfer function, bound of ZVS and parameter design method are given. Adaptive ZVS control strategy guarantees the zero voltage turn-on of switch during the whole process the lamp operation and is effective on various lamps of different manufactures too. Microcontroller AT90PWM2 for lighting helps to improve the performance and simplify the hardware circuit. The prototype of 70W digital electronic ballast for metal halide lamp proves the validity of the proposed topology and control strategy. Operating frequency is beyond 100 kHz and the whole system efficency is 92%.The start-up process is complex because of the characteristic of metal halide lamp. Corresponding control method is applied to the lamp according to features of each stage. One cycle peak current control strategy is proposed to limit the excessive current during commutation period and run-up stage. One cycle peak current contrl strategy and adaptive ZVS control strategy play an important role in each stage. The adaptive ZVS control strategy can not only guarantee the zero voltage turn-on of switch but also satisfy the rapid response requirement in ignition transient state. The average input power control method based on the adjustment of turn-on time is simple and effective. The experiments with different lamps prove the feasibility and accuracy of constant power control strategy.Resonant ignition method enjoys the simple circuit and flexible control but it can not avoid the excessive current. Meanwhile, resonant ignition method is not proper for most of LFSW topology such as single stage topology. In practice, pulse ignition method is adopted in most of the LFSW ballast. The requirements for the pulse ignition circuit are introduced and a new dual frequency trigger pulse ignition circuit is proposed. Circuit model is analysised in detail and the influence of circuit parameters on pulse amplitude and width is given. Peak current is limited and amplitude variation caused by transformer parasitic capacitor torlance is restricted by the auxiliary inductor. The auxiliary inductor and ransformer parasitic capacitor form another resonant circuit. As a result, an igniting pulse sequence with two different frequencies is applied to the lamp and both pulse amplitude and width are guaranteed.更多还原