非理想变压器双开关正激变换器峰值电流控制的小信号分析

针对峰值电流控制的双开关正激变换器，本文提出了一种有效的分析方法，建立了交流小信号模型，并应用这个模型分析了其主要电气特性，得到了如下结论：（1）、峰值电流控制可以大大提高系统对输入电压波动的抑制能力；（2）、峰值电流控制减少了Q值，使系统变为一个低Q值的系统；（3）、峰值电流控制扩展了频带；(4)在采用峰值电流控制的正激变换器设计中，必须考虑励磁电感对系统产生的影响。
关键词：双开关正激变换器  峰值电流控制  小信号模型
Abstract—A small signal analysis approach of a dual forward converter with non-ideal transformer in current-programmed control (CPC) has been investigated in this paper. A small-signal model has been derived to determine the small-signal characteristics of the converter. By employing this model, the following significant features have been revealed or explained: (1). If the artificial ramp slop is properly selected, the ideal line-to-output transfer function of the converter becomes zero. That is to say, the output voltage fluctuation of causing from a perturbation of the DC bus voltage can be substantially restrained; (2). The CPC can greatly reduce the Q-factor and make the converter to become a low Q-factor system; (3). The current-programmed control can extend the bandwidth; (4).The magnetizing inductor plays an important role in the converter, so we must consider it when we design the control circuit.
Keywords—dual forward converter, current-programmed control, small signal model
1、引言
双正激变换器是目前中大功率变换器中应用最多的拓扑之一。它克服了正激变换器中开关电压应力高的缺点，每个开关管的电压只承受输入直流电压；磁复位电路简单，可以保证变压器的可靠磁复位；每一个桥臂都是由一个开关管与一个二极管串联组成，不存在桥臂直通的危险，可靠性高。因此，双正激变换器具有其它变换器无法比拟的优点。
一般情况下，我们在对此类电路分析是将变压器视为理想元件，但实际情况并非如此。图1给出了考虑励磁电感的双开关正激变换器主电路的分析电路。电路中其他元件均为理想元件且电路工作在CCM模式下，占空比D<0.5。