可以加熱的MOSFET

　　功率MOSFET以其低電容和良好的高頻開(kāi)關(guān)特性，在電力電子設(shè)計(jì)中得到了廣泛的應(yīng)用。他們已經(jīng)進(jìn)入了許多應(yīng)用領(lǐng)域，并幫助開(kāi)辟新的應(yīng)用市場(chǎng)，從混合動(dòng)力和電動(dòng)汽車(chē)到太陽(yáng)能到極端環(huán)境探測(cè)。這些環(huán)境的統(tǒng)一因素是熱。汽車(chē)發(fā)動(dòng)機(jī)和太陽(yáng)能電池板能夠產(chǎn)生熱量，使功率器件的結(jié)溫遠(yuǎn)高于100°C。這種熱量會(huì)嚴(yán)重影響功率半導(dǎo)體，而這些半導(dǎo)體并不是用來(lái)應(yīng)付的。

　　功率半導(dǎo)體都有溫度限制。泄漏電流隨著溫度的升高而增加，這會(huì)加速導(dǎo)致?lián)舸l件的影響，從而損壞電路并造成其他危險(xiǎn)。

　　所有半導(dǎo)體額定電壓為一個(gè)給定的最大反向電壓。如果設(shè)備在高于這種電壓的情況下工作，反向偏置電場(chǎng)就會(huì)產(chǎn)生高電場(chǎng)。這些電場(chǎng)足夠強(qiáng)，可以把帶電粒子加速到高能量。當(dāng)這些加速的載流子擊中電子與原子結(jié)合時(shí)，它們轉(zhuǎn)移足夠的能量以破壞原子鍵并形成電子空穴對(duì)。在高電場(chǎng)下，它們會(huì)朝相反的方向加速，并有可能撞擊其他固定電子，使它們自由旋轉(zhuǎn)。結(jié)果是雪崩擊穿，破壞了功率半導(dǎo)體中的二極管層，使器件失去了功能。

　　Even if the device is not irreparably damaged， as some devices are designed to withstand a certain amount of avalanche current， a hysteresis effect means the voltage has to drop significantly before the reverse current is shut off， potentially causing damage to other components in the system.

　　In silicon， heat tends to accelerate the process of avalanche breakdown because higher temperatures will impart thermal energy to valence electrons in the crystal lattice of the power device. As more thermal energy is absorbed， some of those valence electrons will break free of their bonds and move into the conduction bands. Inductive loads increase the risk of breakdown because of the high reverse-bias conditions they can impose on the diode junctions inside a power transistor when used with switching power-supply circuitry.