非理想變壓器雙開關(guān)正激變換器峰值電流控制的小信號分析

針對峰值電流控制的雙開關(guān)正激變換器，本文提出了一種有效的分析方法，建立了交流小信號模型，并應(yīng)用這個模型分析了其主要電氣特性，得到了如下結(jié)論：（1）、峰值電流控制可以大大提高系統(tǒng)對輸入電壓波動的抑制能力；（2）、峰值電流控制減少了Q值，使系統(tǒng)變?yōu)橐粋€低Q值的系統(tǒng)；（3）、峰值電流控制擴(kuò)展了頻帶；(4)在采用峰值電流控制的正激變換器設(shè)計(jì)中，必須考慮勵磁電感對系統(tǒng)產(chǎn)生的影響。
關(guān)鍵詞：雙開關(guān)正激變換器? 峰值電流控制? 小信號模型
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
雙正激變換器是目前中大功率變換器中應(yīng)用最多的拓?fù)渲弧Ｋ朔苏ぷ儞Q器中開關(guān)電壓應(yīng)力高的缺點(diǎn)，每個開關(guān)管的電壓只承受輸入直流電壓；磁復(fù)位電路簡單，可以保證變壓器的可靠磁復(fù)位；每一個橋臂都是由一個開關(guān)管與一個二極管串聯(lián)組成，不存在橋臂直通的危險(xiǎn)，可靠性高。因此，雙正激變換器具有其它變換器無法比擬的優(yōu)點(diǎn)。
一般情況下，我們在對此類電路分析是將變壓器視為理想元件，但實(shí)際情況并非如此。圖1給出了考慮勵磁電感的雙開關(guān)正激變換器主電路的分析電路。電路中其他元件均為理想元件且電路工作在CCM模式下，占空比D<0.5。