五、新型說明： 【新型所屬之技術領域】 本創作係有關-種降㈣切換式電源供應器及其控制 電路，特別是指-種_輸出端電流以控制輸人電壓輸出電 壓間轉換讀麵娜錢源縣H及其控制電路。 【先前技術】V. New description: [New technical field] This creation is related to the type of (four) switching power supply and its control circuit, especially the type-output current to control the input voltage between the output voltage Na Qianyuan County H and its control circuit. [Prior Art]
第1圖係示出先前技術之降㈣娜式轉供應器 之示意圖。降壓型切換式電源供應器1G將—輸入電壓I 轉換為-輸出電壓V〇ut，即將較高的輸入電壓轉換成較低 的輸出電壓，並對電池Bat進行充電。 _ 功平級14包括 -- 例问關W1、卜橋開關Q2及電感l， 該三個7€件共同連接於一切換節點N2。輸入電壓W供 應之電流會經過上橋開關Φ、電感L及電阻RS，再汽向' 輸出電壓Vout所在之輸出端，可使電池Bat充電。輸^ 流偵測電路18會债測電阻Rs兩端節點N3及N4之壓降， 並根據該壓降計算經過電阻RS之輸出電流，從而輸出一 代表輸出電紅職AlGut。她地，輸人電輸則電路 17會個亡橋開關Q1兩端節點州及犯之壓降，並根 該壓降計算經過其之輸人電流，從而輸出—代表輸入電流 之訊號Aim。輸出電_測電路19會偵測輸出端之輸出 電壓V〇Ut，並輸出一代表輸出電壓之訊號AVom。驅動電 路丄1會根據前述訊號她、編及鳥世產生控制上摘 開關Q1及下橋開關Q2之開關訊號，以控制輸 輸出電壓Vout間的轉換。 然該電阻RS會隨著溫度而改變電阻值，而且不同電降 之電阻值亦有相§變異，因此訊號AIGUt往往無法正確代 表輸出電流’從而造成驅動電路】j難以準確地控制上橋開 關Q1及下橋開關Q2之開關。此外，電池Bat可能會產生 漏電流’逆向細下橋關Q2，造成充電解的損失。 有鑑於以上所述，本創作即針對先前技術之不足，提 出種月b正確谓測輸出端電流以控制輸入電壓輸出電麗 間轉換之降㈣切換式電源供應^及其控織路，且能避 ^電流回流，以改善電壓轉換之不準確及逆電流的問 題0 【新型内容】 。。本新型目的之一在提供一種降壓型切換式電源供應 器。 本新型的另一目的在提供一種降壓型切換式電源供 應器之控制電路。 為達上述之目的，本創作提供了一種降壓型切換式電 源供應器，將-輸入電壓轉換為一輸出電壓，包含：一功 率包^-上橋開關、一下橋開關及一電感，共同連接 /刀換節點’其中該上橋開關電性連接於該輸入電壓、 -亥下橋開關電性連接於地；一電晶體，電連接於該電感與 =輸出電壓之間，其中該電晶體具有—本體二極體，其方 向可阻擋自該輸出電壓流往該下橋關之逆電流；以及一 。電路至夕根據經過該電晶體之電流，控制該上橋開 關及該下橋開關之摞作。 就另個觀點言，本新型提供了 一種降壓型切換式電 原供應器之控制電路’調整通過—電感之電流以對一輸出 M442648 輸出電壓之訊號AVout。驅動電路21會根據前述訊號 Alin、Alout及AVout產生控制上橋開關qi及下橋開關 Q2之開關訊號’以控制輸入電壓Vin輸出電壓Vout間轉 換。 本實施例中’輸出電流偵測電路28包括誤差放大器 281及282 ’其中誤差放大器281萃取該電晶體Q3兩端之 電壓差’且誤差放大器282將該電壓差與一第一參考訊號 Vrefl比較，以產生訊號Alout。相似地，輸入電流偵測電 路27包括誤差放大器271及272，其中誤差放大器271萃 取該上橋開關Q1兩端之電壓差，又誤差放大器272將該 電麼差與一第二參考訊號Vref2比較以產生訊號A!in。輸 出電壓偵測電路29係一誤差放大器，會偵測輸出端之輸 出電壓Vout ’並與第三參考訊號Vref3比較而輸出訊號 AVout。輸入電流偵測電卷27、輸出電流偵測電路28及輸 出電壓偵測電路29並不受此實施例之例示限制，而可以 是其他等效電路或元件所構成。 本實施例中驅動電路21包括一 PWM控制器211、 一類比總和電路212及一驅動級213。類比總和電路212 加總或以其他方式組合前述訊號AIin、AI〇ut及AV〇ut，並 輸出訊號至PWM控制器21卜PWM控制器.211會產生工 作訊號，.而驅動級213根據該工作訊號，驅動上橋開關Q1 及下橋開關Q2。驅動電路21並不受此實施例之例示限 制’或可以是其他等效電路或元件所構成，例如，驅動上 橋開關Q1及下橋開關Q2的方式可以為定頻或變頻，又驅 動電路21除了取得代表輸出電流之訊號Alout外，並不必 須一定要取得訊號AIin及AV〇ut，等等。上橋開關卩卜 M442648 下橋開關Q、電晶體Q3、輸人電流偵測電路27、輸出電 流债測電路28及輸出電壓偵測電路29 合至-控制電路25内，而該控制電路25與+電導:= 他元件(例如：電料)組合成為魏供絲2()。若上橋開 關Q1及下橋開關Q2為高功率電晶體，亦可將該兩開關自 控制電路25移出至外部。 第3圖示出本創作降壓型切換式電源供應器的另一 個實施例。降壓翻換式電源供卿3G包含—驅動電路 2卜-功率級24、-電晶體q3、一輸入電流_電路27、 -輸出電流細電路該28、-輸出電壓細電路29及兩 電壓產生盗(32、33)。當上橋開關φ及電晶體印係刪 電晶體’财瞧電壓需要高於源極之賴才能被開啟， 故電壓產生H(32、33)可以提供所需電壓。該電壓產生器 (32、33)可以是電荷泵或勒:帶式電容電路。 上橋開關Q卜下橋開關q、電晶體φ、輸入電流價 測電路27、輸出電流债測電路28、輸出電壓偵測電路29 及電壓產生器(32、33)可以半導體製程整合至― 内，而該控制電路與電感L或其他元件(例如：二電容等） 組^成為電源供應器3G。若上橋開關Q1及下橋開關Q2 為高功率電晶體’亦可將該_關自控制電路移出 部。 以上已針對較佳實施例來說明本創作，唯以上所述 者，僅係為使熟悉本技術者易於了解本創作的内容而已 並非用來限定本_之_制。在本創作之相同精神 了 ’熟悉本技術者可以思及各種等效變化。例如本新型例 示之開關組合或誤差放大器組合可以其他等效之電路戋 8Figure 1 is a schematic illustration of a prior art drop (four) Na-turn supply. The step-down switching power supply 1G converts the input voltage I into an output voltage V〇ut, which converts the higher input voltage into a lower output voltage and charges the battery Bat. The _ level 14 includes -- an example of the W1, the bucking switch Q2 and the inductor l, which are commonly connected to a switching node N2. The current supplied by the input voltage W passes through the upper bridge switch Φ, the inductor L and the resistor RS, and then flows to the output end where the output voltage Vout is located, so that the battery Bat can be charged. The flow detection circuit 18 measures the voltage drop across the nodes N3 and N4 of the resistor Rs, and calculates the output current through the resistor RS according to the voltage drop, thereby outputting a representative electric output AlGut. She, the input power circuit 17 will be the end of the bridge switch Q1 node state and the pressure drop, and the voltage drop is calculated by the input current, and thus the output - the signal Aim representing the input current. The output power measuring circuit 19 detects the output voltage V〇Ut of the output terminal and outputs a signal AVom representing the output voltage. The driving circuit 丄1 will control the switching between the switch Q1 and the lower bridge switch Q2 according to the above-mentioned signals, her and the bird to control the conversion between the output voltage Vout. However, the resistor RS changes the resistance value with temperature, and the resistance values of different electrical drops also have § variation, so the signal AGIout often fails to correctly represent the output current', thereby causing the driving circuit to be difficult to accurately control the upper bridge switch Q1. And the switch of the lower bridge switch Q2. In addition, the battery Bat may generate a leakage current, which reverses the bridge Q2, causing a loss of the charging solution. In view of the above, this creation is aimed at the shortcomings of the prior art, and proposes that the type of month b correctly predicts the output current to control the input voltage output and the conversion between the electric and the electric (the) switching power supply ^ and its control weaving, and Avoid current reflow to improve the inaccuracy of voltage conversion and reverse current problem [New content]. . One of the novel objects is to provide a step-down switching power supply. Another object of the present invention is to provide a control circuit for a step-down switching power supply. For the above purposes, the present invention provides a step-down switching power supply that converts an input voltage into an output voltage, including: a power pack, an upper bridge switch, a lower bridge switch, and an inductor, which are commonly connected. a switch node, wherein the upper bridge switch is electrically connected to the input voltage, and the lower bridge switch is electrically connected to the ground; a transistor is electrically connected between the inductor and the output voltage, wherein the transistor has a body diode whose direction blocks the reverse current flowing from the output voltage to the lower bridge; and one. The circuit controls the operation of the upper bridge switch and the lower bridge switch according to the current passing through the transistor. In another aspect, the present invention provides a control circuit for a step-down switching power supply device that adjusts the current through the inductor to output a voltage AVout to an output M442648. The driving circuit 21 generates a switching signal _ for controlling the upper bridge switch qi and the lower bridge switch Q2 according to the signals Alin, Alout and AVout to control the conversion between the input voltage Vin output voltage Vout. In the present embodiment, the output current detecting circuit 28 includes error amplifiers 281 and 282 'where the error amplifier 281 extracts the voltage difference across the transistor Q3' and the error amplifier 282 compares the voltage difference with a first reference signal Vref1. To generate the signal Alout. Similarly, the input current detecting circuit 27 includes error amplifiers 271 and 272, wherein the error amplifier 271 extracts the voltage difference across the upper bridge switch Q1, and the error amplifier 272 compares the power difference with a second reference signal Vref2. Generate signal A!in. The output voltage detecting circuit 29 is an error amplifier that detects the output voltage Vout' of the output terminal and compares it with the third reference signal Vref3 to output a signal AVout. The input current detecting coil 27, the output current detecting circuit 28, and the output voltage detecting circuit 29 are not limited by the exemplification of this embodiment, but may be constituted by other equivalent circuits or components. The driving circuit 21 in this embodiment includes a PWM controller 211, an analog sum circuit 212, and a driving stage 213. The analog sum circuit 212 adds or otherwise combines the aforementioned signals AIin, AI〇ut, and AV〇ut, and outputs a signal to the PWM controller 21, which generates a working signal, and the driver stage 213 operates according to the work. The signal drives the upper bridge switch Q1 and the lower bridge switch Q2. The driving circuit 21 is not limited by the exemplification of this embodiment' or may be other equivalent circuits or components. For example, the manner of driving the upper bridge switch Q1 and the lower bridge switch Q2 may be fixed frequency or frequency conversion, and the driving circuit 21 In addition to obtaining the signal Alout representing the output current, it is not necessary to obtain the signals AIin and AV〇ut, and so on. The upper bridge switch M M442648 lower bridge switch Q, transistor Q3, input current detecting circuit 27, output current debt detecting circuit 28 and output voltage detecting circuit 29 are integrated into the control circuit 25, and the control circuit 25 is + Conductance: = The combination of his components (for example: electric material) becomes Wei Wei 2 (). If the upper bridge switch Q1 and the lower bridge switch Q2 are high power transistors, the two switches can also be removed from the control circuit 25 to the outside. Fig. 3 shows another embodiment of the present step-down switching power supply. The step-down switching power supply for the 3G includes - the drive circuit 2 - the power stage 24, the transistor q3, an input current _ circuit 27, - the output current fine circuit 28, the output voltage fine circuit 29 and the two voltage generation Pirates (32, 33). When the upper bridge switch φ and the transistor printed circuit are required to be turned on higher than the source, the voltage generation H (32, 33) can supply the required voltage. The voltage generator (32, 33) can be a charge pump or a band: capacitive circuit. The upper bridge switch Q, the lower bridge switch q, the transistor φ, the input current price measuring circuit 27, the output current debt measuring circuit 28, the output voltage detecting circuit 29, and the voltage generator (32, 33) can be integrated into the semiconductor process. And the control circuit and the inductor L or other components (for example, two capacitors, etc.) become the power supply 3G. If the upper bridge switch Q1 and the lower bridge switch Q2 are high power transistors, the _ off control circuit can also be removed. The present invention has been described above with respect to the preferred embodiments, and the above description is merely for the purpose of making the content of the present invention easy for those skilled in the art to understand the present invention. In the same spirit of this creation, the person familiar with the technology can think of various equivalent changes. For example, the switch combination or error amplifier combination of the present exemplary embodiment can be other equivalent circuits 戋 8