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  • Suppose we want to increase the voltage of our only battery.

    假設我們要增加唯一電池的電壓。

  • We have an inductor, a transistor, a diode, and a capacitor.

    我們有一個電感器,一個晶體管,一個二極管和一個電容器。

  • We also have a device to which we have to deliver power,

    我們還有一個必須向其供電的設備,

  • represented here by a light bulb.

    這裡用燈泡表示。

  • The connection to the gate of the transistor is not shown,

    未顯示到晶體管柵極的連接,

  • but this is a voltage that we control.

    但這是我們控制的電壓

  • Suppose we control this gate voltage in a way such that

    假設我們以某種方式控制該柵極電壓

  • the transistor behaves like a switch, which we can turn on or off.

    晶體管的行為就像一個開關,我們可以打開或關閉它。

  • If we close the switch, we will cause a DC voltage to appear across the inductor.

    如果關閉開關,將導致直流電壓出現在電感兩端。

  • The current through the inductor will keep increasing,

    通過電感的電流將持續增加,

  • so long as the switch is closed.

    只要開關閉合即可。

  • The current through an inductor can not change instantaneously.

    流過電感的電流不能瞬時改變。

  • Therefore the moment we open the switch,

    因此,當我們打開開關的那一刻,

  • the inductor will create a force causing the current to continue flowing.

    感應器將產生一個力,使電流繼續流動。

  • Suppose we keep turning the switch on and off.

    假設我們一直打開和關閉開關。

  • By continuously turning the switch on and off,

    通過持續打開和關閉開關,

  • we have created a DC output voltage at the light bulb

    我們在燈泡上創建了直流輸出電壓

  • that is higher than the voltage of the battery.

    高於電池電壓。

  • We call this a “Boost Converter.”

    我們稱其為“升壓轉換器”。

  • We can control the value of the DC output voltage at the light bulb

    我們可以控制燈泡的直流輸出電壓值

  • by controlling the percentage of time that this switch is on.

    通過控制此開關打開的時間百分比。

  • Suppose that we leave the switch off all the time.

    假設我們一直關閉開關。

  • With the switch off 100% of the time,

    在100%的時間關閉電源的情況下,

  • the output voltage will equal the voltage of the battery.

    輸出電壓將等於電池的電壓。

  • What if we instead have the switch on most of the time?

    如果我們大多數時候都打開電源怎麼辦?

  • If the switch is almost always on,

    如果開關幾乎總是打開,

  • then assuming we have ideal components,

    然後假設我們有理想的組件,

  • the current will theoretically keep increasing to infinity.

    從理論上講,電流將繼續增加到無窮大。

  • During the brief moment when we turn the switch off,

    在短暫的時間內,當我們關閉開關時,

  • an infinite current would charge the capacitor to an infinite voltage.

    無限大的電流會將電容器充電至無限大的電壓。

  • By selecting the appropriate percentage of time that the switch is on,

    通過選擇開關打開的適當時間百分比,

  • we can set the output voltage to any value that is larger than the battery voltage.

    我們可以將輸出電壓設置為大於電池電壓的任何值。

  • But, we will need a different circuit to produce a

    但是,我們將需要不同的電路來產生

  • steady state output voltage that is smaller than the battery voltage.

    穩態輸出電壓小於電池電壓。

  • At first, this may seem simple,

    首先,這似乎很簡單,

  • as this can be done by using resistors to create a voltage divider.

    因為這可以通過使用電阻器創建分壓器來完成。

  • But, the problem is that we want to be efficient,

    但是,問題是我們要提高效率,

  • and resistors dissipate energy as heat.

    電阻將能量耗散為熱量。

  • Any energy that is lost as heat in a resistor

    電阻中作為熱量損失的任何能量

  • is not delivered to the device which we wish to power.

    沒有交付給我們希望供電的設備。

  • If we don't care about efficiency,

    如果我們不在乎效率,

  • but just want to be able to adjust the output voltage,

    但只想能夠調整輸出電壓,

  • we can do it through a circuit such as this one.

    我們可以通過這樣的電路來做到這一點。

  • The energy lost as heat in the transistor is the voltage across the transistor,

    由於晶體管中的熱量而損失的能量是晶體管兩端的電壓,

  • multiplied by the current passing through it.

    乘以通過它的電流。

  • Now, consider the following.

    現在,考慮以下內容。

  • If we operate and think of the transistor as an ideal switch,

    如果我們操作並認為晶體管是理想的開關,

  • then when the switch is off, the current is zero

    然後,當開關斷開時,電流為零…

  • And when the switch is on, the voltage across it is zero.

    當開關接通時,其兩端的電壓為零。

  • Therefore, in theory, if the transistor is either fullyonor fullyoff”,

    因此,理論上,如果晶體管完全“導通”或完全“截止”,

  • and never somewhere in between, the voltage multiplied by the current is always zero,

    而且介於兩者之間的任何地方,電壓乘以電流始終為零,

  • and there is no energy dissipated as heat in the transistor.

    而且晶體管中沒有能量作為熱量散發。

  • But, if we want to be 100% efficient, we also have to get rid of the resistor.

    但是,如果我們想提高效率100%,則還必須去除電阻器。

  • Suppose that in this circuit, we always operate the transistor as an ideal switch.

    假設在此電路中,我們始終將晶體管用作理想開關。

  • If we keep opening and closing the switch,

    如果我們繼續打開和關閉開關,

  • theaveragevoltage across the light bulb

    燈泡上的“平均”電壓

  • will be less than the voltage of the battery,

    將小於電池的電壓,

  • but this is only because the voltage across the light bulb

    但這僅僅是因為燈泡兩端的電壓

  • is zero when the switch is open.

    開關斷開時為零。

  • We can try to prevent the voltage from dropping to zero

    我們可以嘗試防止電壓降至零

  • by adding a capacitor across the light bulb.

    通過在燈泡兩端增加一個電容器。

  • But now, when we close the switch,

    但是現在,當我們關閉開關時,

  • we are trying to change the voltage of a capacitor instantaneously,

    我們正在嘗試立即更改電容器的電壓,

  • which is impossible.

    這是不可能的。

  • As a result, an extremely large current will flow to charge the capacitor,

    結果,將流過非常大的電流來為電容器充電,

  • and this can cause considerable damage.

    這會造成相當大的損害。

  • We can try to reduce this current by adding a resistor.

    我們可以嘗試通過添加一個電阻來減小此電流。

  • But, as we said before, we do not want a resistor

    但是,正如我們之前所說,我們不需要電阻

  • because resistors dissipate energy as heat.

    因為電阻將能量耗散為熱量。

  • Instead of using a resistor, we can limit the current by using an inductor.

    代替使用電阻器,我們可以通過使用電感器限制電流。

  • An ideal inductor does not dissipate energy as heat.

    理想的電感器不會將能量耗散為熱量。

  • But, since the current through an inductor can't change instantaneously,

    但是,由於流過電感的電流不能瞬時變化,

  • the inductor will force the current to keep flowing through the switch

    電感器將迫使電流保持流過開關

  • even after we open it, which is an extremely dangerous phenomena.

    即使我們打開它,這也是一個極其危險的現象。

  • We can prevent the current from flowing through the open switch by adding a diode.

    我們可以通過增加一個二極管來防止電流流過斷開的開關。

  • The diode will give the current a different path to flow through.

    二極管將為電流提供不同的流過路徑。

  • We call this circuit a “Buck converter.”

    我們將此電路稱為“降壓轉換器”。

  • We can control the value of the DC output voltage at the light bulb

    我們可以控制燈泡的直流輸出電壓值

  • by controlling the percentage of time that this switch is on.

    通過控制此開關打開的時間百分比。

  • This allows us to create any DC voltage at the light bulb

    這使我們可以在燈泡上產生任何直流電壓

  • that is lower than the voltage of the battery.

    低於電池電壓。

  • Assuming that we had ideal components, this circuit would be 100% efficient.

    假設我們有理想的組件,則該電路的效率為100%。

  • This is because ideal capacitors, ideal inductors, and ideal switches

    這是因為理想的電容器,理想的電感器和理想的開關

  • do not dissipate any energy as heat.

    不要耗散任何能量作為熱量。

  • We are thinking of the transistor as an ideal switch.

    我們認為晶體管是理想的開關。

  • An ideal diode can also be thought of as a switch.

    理想的二極管也可以認為是開關。

  • The diode is anoff switchwhen it is blocking current

    當二極管阻止電流時,它是一個“關斷開關”

  • from flowing in the reverse direction,

    不會反向流動

  • and the diode is anon switchwhen current flows in the forward direction.

    當電流正向流動時,二極管為“導通開關”。

  • The Buck converter uses the exact same components

    Buck轉換器使用完全相同的組件

  • as the Boost converter, just arranged differently.

    作為Boost轉換器,只是佈置不同。

  • In the real world, of course, these components are not ideal,

    當然,在現實世界中,這些組件並不理想,

  • and they do in fact dissipate power.

    實際上,它們確實在消耗功率。

  • Therefore, to maximize efficiency, actual power converts

    因此,為了最大化效率,實際功率會轉換

  • are typically more complicated than the circuits shown here.

    通常比這裡顯示的電路複雜。

  • But, the basic principles are the same.

    但是,基本原理是相同的。

  • These basic principles are that transistors are operated as switches.

    這些基本原理是將晶體管用作開關。

  • We never try to change the voltage across a capacitor instantaneously.

    我們永遠不會嘗試立即改變電容器兩端的電壓。

  • And we never try to change the current through an inductor instantaneously.

    而且,我們絕不會嘗試立即改變通過電感器的電流。

  • Much more information is available in the other videos on this channel,

    該頻道的其他視頻提供了更多信息,

  • and please subscribe for notifications when new videos are ready.

    當新視頻準備就緒時,請訂閱通知。

Suppose we want to increase the voltage of our only battery.

假設我們要增加唯一電池的電壓。

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升壓變換器與降壓變換器 - 電力電子

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    Amy.Lin 發佈於 2021 年 01 月 06 日
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