寄生電容影響升壓變壓器的設(shè)計

　　升壓設(shè)計中最關(guān)鍵的部件之一像圖1是變壓器。變壓器的寄生組件，可以使他們偏離它們的理想特性和寄生電容與二次關(guān)聯(lián)可引起大共鳴開關(guān)電流前沿的電流尖峰波形。這些尖峰可以導(dǎo)致調(diào)節(jié)器顯示表現(xiàn)為義務(wù)的不穩(wěn)定的操作條件周期不穩(wěn)定。這種影響是非常高的加劇電壓設(shè)計。重視變壓器設(shè)計將治愈這個問題。

　　圖2顯示了高頻電流路徑的寄生電容。在操作假設(shè)分析中輸入和輸出電壓在交流地。因此，該寄生電容并聯(lián)。變壓器的次級提供這些電容器的交流電流路徑。流經(jīng)次級產(chǎn)品的電流N倍于初級電流。由于寄生電容匝數(shù)比增大，初級電流逐漸變大。

　　The operation waveforms for this circuit are shown in Figure 3. When the switch （VSW pin—Trace A） is turned “on” the primary is pulled to ground. The secondary cannot instantly follow this action because of the loading effects of its parasitic capacitors. The effects of the parasitic capacitance can easily be seen in the leading edge of the switch current waveform （Trace B）。 This current spike is caused by the loading effect of the secondary parasitic capacitances. The secondary output （Trace D） swing can exceed 600V. As such， a large amount of charge （Q = C ? V） is needed to swing this node during the switching transients.