201220666 六、發明說明： 【發明所屬之技術領域】 本發明係有關於一種同步整流器，尤指一種採用 電流變壓器偵測流經金氧半電晶體（MOSFET)的順向 電流並產生驅動MOSFET之訊號，並藉由該電流變壓器 洩磁回復觸動關斷開關以加速MOSFET截止，而不會有 逆電流產生之同步整流器。 【先前技術】 φ —般的電源轉換器大多採用功率二極體整流方 法，然而對於低輸出電壓高電流的電源轉換器，往往在 整流一極體上產生很大的熱及功率損失’因而使效率下 降’近年來由於金氧半場效電晶體（MOSFET)製程能 力的提升’陸續研發量產高功率低導通電阻的 MOSFET，使切換式電源轉換器轉換效率能大幅度的提 升’不過MOSFET為電壓驅動控制元件，當轉換器工作 於不連續電流模式時，會產生逆流問題而造成輕載或空 載時增加功率損耗，而造成能源的浪費。 • 在電源轉換器領域中，一般皆需要使用整流二極 體於變塵器二次側’將變壓器傳送的交流功率轉換成直 流功率，如何降低整流器的功率損失是近年來研究重要 的方向，採用電流變壓器驅動MOSFET元件也是有很多 種方式，如第十一圖所示，係顯示美國專利號US6134131 的一種習知的同步整流器，其係採用電流變壓器產生驅 動MOSFET的信號，並增加一個磁滯驅動器驅動 MOSFET ’且利用電流變壓器第三線圈將額外能量耦合 到外部定電壓源產生鉗制電壓功能，不僅可以將能量回 送至外部定電壓源亦可鉗制第二線圈的電壓使 201220666 MOSFET閘極驅動電壓能穩定於安全範圍，第四線圈提 供變壓器磁的重置回路同時使產生第二線圈產生反向 電壓透過磁滯驅動器關斷MOSFET，此同步整流器雖可 正確驅動MOSFET將電流變壓器產生的能量回送，亦可 透過磁滯驅動器增加驅動電流及降低切換損失，但電流 變壓器需要四個線圈繞組，且需要外部電源及磁滯驅動 器等，故同步整流器線路架構複雜，加工裝配不易，增 加成本’相對於一般的二極體整流器只有二個接腳，比 較易於使用。 請參考第十二圖係顯示美國專利號 US6813166B1的一種習知的同步整流電源轉換器，其係 採用電流變壓器控制的同步整流電源轉換器，此電路主 要應用於返馳式轉換器，當電流通過電流變壓器一次側 時，二次側線圈感應出正向電壓提供給驅動單元以驅動 導通電晶體Q4，以使同步開關MOSFET導通，當電流 變壓器一次側電流為零時，二次側線圈產生負電壓而令 第二電晶體轉為導通狀態，繼而驅動PNP電晶體Q5導 通，而關斷同步開關MOSFET，故此同步整流器必須有 電流變壓器，正向驅動電晶體Q1，逆向驅動電晶體Q2， 驅動單元（電晶體Q4及Q5)，及外加的電源提供給驅動 單元等，雖改善美國專利號US6134131的電流變壓器需 要多組線圈,的缺點，但額外卻增加多個驅動電晶體。 因此，如何改善習知技術存在之缺失以及減少成 本，實為本產業亟待解決之問題。 【發明内容】 有鑑於此，本發明揭示一種由電流變壓器直接驅 動同步開關的同步整流器，此同步整流器可模組化，以 提供如傳統的整流二極體P極與N極接腳，同時能工作 201220666 於連續或非連續電流模式，降低導通損失，適用於各種 電源轉換器拓樸如返馳式轉換器、順向式轉換器及全 (半）橋式轉換器等。 本發明之目的在於提供一種同步整流器，係藉 由電流變壓器驅動同步整流開關，將交流的功率轉換成 直流，以降低功率損耗及提高效率。 本發明之另一目的在於提供一模組化之同步整 流器，以提供如傳統整流二極體P極與N極接腳，以適 合應用於各種電源轉換器拓樸。 本發明之再一目的在於提供一種可應用於連續 或非連續之電流模式之同步整流器。 達到上述目的之本發明同步整流器，包含：一同 步整流開關，用以導通或關斷通過之電流；一電流變壓 器，具有一次側線圈及二次側線圈，該一次側線圈與該 同步整流開關串聯，且用以通過順向導通電流，而該二 次側線圈係感應順向電流，且用以提供信號驅動及關斷 同步整流開關；一驅動穩壓電路，係連接至該電流變壓 器之二次側線圈，且用以將二次側感應出的順向電流轉 換成驅動該同步整流開關之驅動信號，以鉗制該二次側 線圈的感應電壓；一關斷開關，係與該同步整流開關連 接，且用以當該順向電流截止時，將該同步整流開關關 斷；一關斷信號偵測電路，係與該電流變壓器之二次側 線圈及該關斷開關連接，且用以偵測該電流變壓器一次 側電流為零時，使該二次側線圈產生重置電壓，以觸動 該關斷開關導通；及一驅動保持電路，係連接於該同步 整流開關，且用以將該驅動穩壓電路所轉換之驅動信 號，保持至該關斷開關導通前。 該同步整流開關為金氧半場效電晶體 201220666 (MOSFET)，且内含一本體二極體，或於汲極與源極之 間外加一本體二極體。 該驅動.穩壓電路包括一二極體及一稽納二極 體，該二極體之陽極連接至該電流變壓器二次側線圈之 正極端，而該二極體之陰極連接至該稽納二極體之陰極 端，用以偵測該電流變壓器二次側電流，而該稽納二極 體之陽極端連接至該電流變壓器二次側線圈之負極 端，用以鉗制該電流變壓器二次側感應的電壓。 該驅動保持電路包括一電容器及一電阻器，該電 容器與電阻器並聯，且該電容器及電阻器之一端連接於 該同步整流開關之閘極，而該電容器及電阻器之另一端 則連接於該同步整流開關之源極，當該同步整流開關無 閘極驅動信號能自然洩放閘極能量。 該電容器為閘極的輸入等效電容或外加的實體 電容器。 該關斷信號偵測電路包括一電容器及一電阻 器，該電容器與該電阻器串聯，且該電容器連接於該電 壓變壓器二次側線圈之正極端，而該電阻器一端連接至 該關斷開關與該電容器，而該電阻器之另一端則與該電 流變壓器之一次側線圈之負極端連接，用以偵測關斷信 號。 該關斷開關為一 PNP型電晶體，其基極連接至 該關斷信號偵測電路，且其射極連接至該同步整流開關 之閘極，而其集極連接至同步整流開關之源極。 【實施方式】 請參考第一圖，係顯示本發明同步整流器之電路 圖。本發明同步整流器100,包含：一電流變壓器101、 201220666 一同步整流開關102、一驅動穩壓電路1〇3、一驅動保 持電路104、一關斷信號制電路1〇5及一關斷開關 106,其中該電流變壓n 1G1具有—次側線圈及二次側 線圈，該一次側線圈的一端為卩極，而另—端連接至該 同步整流開關102之源極，而該二次侧線圈的二端則連 接有去磁電阻（R1 )，以提供該電流變壓器去磁 回路，且該二次側線圈之正極性線圈端連接至一電汽 側二極體（D1)。 1201220666 VI. Description of the Invention: [Technical Field] The present invention relates to a synchronous rectifier, and more particularly to a current transformer for detecting a forward current flowing through a metal oxide semiconductor (MOSFET) and generating a signal for driving the MOSFET And the current transformer bleeds back to activate the turn-off switch to accelerate the MOSFET turn-off without the synchronous rectifier generating the reverse current. [Prior Art] Most power converters of φ use power diode rectification methods. However, for low output voltage and high current power converters, large heat and power losses are often generated on the rectifying body. Decreased efficiency 'In recent years, due to the improved process capability of metal oxide half-field effect transistors (MOSFETs), the development of high-power, low-on-resistance MOSFETs has enabled the conversion efficiency of switching power converters to be greatly improved. When the converter is operated in the discontinuous current mode, a reverse current problem occurs, which causes an increase in power loss at light load or no load, resulting in waste of energy. • In the field of power converters, it is generally necessary to use a rectifying diode on the secondary side of the dust collector to convert the AC power transmitted by the transformer into DC power. How to reduce the power loss of the rectifier is an important research direction in recent years. Current transformers also drive MOSFET components in a number of ways, as shown in Figure 11, which shows a conventional synchronous rectifier of the US Pat. No. 6,134,131, which uses a current transformer to generate a signal for driving a MOSFET and adds a hysteresis driver. Drive the MOSFET' and use the third coil of the current transformer to couple the extra energy to the external constant voltage source to generate the clamp voltage function, which can not only return the energy to the external constant voltage source but also clamp the voltage of the second coil to make the 201220666 MOSFET gate drive voltage Stable in the safe range, the fourth coil provides the transformer magnetic reset circuit and the second coil generates the reverse voltage through the hysteresis driver to turn off the MOSFET. The synchronous rectifier can correctly drive the MOSFET to return the energy generated by the current transformer. Drive can be added via hysteresis driver Flow and reduce switching loss, but the current transformer needs four coil windings, and requires external power supply and hysteresis driver, so the synchronous rectifier circuit structure is complicated, processing and assembly is not easy, and the cost is increased. Compared with the general diode rectifier, there are only two. The pins are easier to use. Please refer to the twelfth figure showing a conventional synchronous rectification power converter of US Pat. No. 6,831,166 B1, which is a synchronous rectifier power converter controlled by a current transformer, which is mainly applied to a flyback converter when current is passed. When the current transformer is on the primary side, the secondary side coil induces a forward voltage to be supplied to the driving unit to drive the conduction current crystal Q4 to turn on the synchronous switching MOSFET. When the primary side current of the current transformer is zero, the secondary side coil generates a negative voltage. The second transistor is turned into a conducting state, which in turn drives the PNP transistor Q5 to turn on, and turns off the synchronous switching MOSFET. Therefore, the synchronous rectifier must have a current transformer, forward drive transistor Q1, reverse drive transistor Q2, and drive unit ( The transistors Q4 and Q5), and the external power supply are supplied to the driving unit and the like. Although the current transformer of the US Pat. No. 6,134,131 is required to have multiple sets of coils, the additional driving transistors are additionally added. Therefore, how to improve the lack of conventional technology and reduce costs is an urgent problem for the industry. SUMMARY OF THE INVENTION In view of this, the present invention discloses a synchronous rectifier that directly drives a synchronous switch by a current transformer, and the synchronous rectifier can be modularized to provide a P-pole and an N-pole of a conventional rectifier diode, and at the same time Work 201220666 Reduces conduction losses in continuous or discontinuous current mode, suitable for a variety of power converter topologies such as flyback converters, forward converters and full (semi) bridge converters. SUMMARY OF THE INVENTION It is an object of the present invention to provide a synchronous rectifier which converts alternating current power into direct current by means of a current transformer to drive a synchronous rectification switch to reduce power loss and improve efficiency. Another object of the present invention is to provide a modular synchronous rectifier that provides, for example, conventional rectifier diode P and N pole pins for use in a variety of power converter topologies. It is still another object of the present invention to provide a synchronous rectifier that can be applied to a continuous or discontinuous current mode. The synchronous rectifier of the present invention achieves the above object, comprising: a synchronous rectification switch for turning on or off the current passing through; a current transformer having a primary side coil and a secondary side coil, the primary side coil being connected in series with the synchronous rectification switch And used to pass the forward current, and the secondary side coil senses the forward current, and is used to provide a signal to drive and turn off the synchronous rectifier switch; a drive voltage regulator circuit is connected to the current transformer twice a side coil for converting a forward current induced by the secondary side into a driving signal for driving the synchronous rectifying switch to clamp the induced voltage of the secondary side coil; and a shutdown switch connected to the synchronous rectifying switch And when the forward current is cut off, the synchronous rectification switch is turned off; a shutdown signal detection circuit is connected to the secondary side coil of the current transformer and the shutdown switch, and is used for detecting When the primary side current of the current transformer is zero, the secondary side coil generates a reset voltage to activate the turn-off switch to be turned on; and a driving and holding circuit is connected And the synchronous rectification switch is configured to maintain the driving signal converted by the driving voltage stabilization circuit until the shutdown switch is turned on. The synchronous rectification switch is a gold-oxygen half-field transistor 201220666 (MOSFET) and includes a body diode or a body diode between the drain and the source. The driving voltage regulator circuit comprises a diode and a gate diode, the anode of the diode is connected to the positive terminal of the secondary side coil of the current transformer, and the cathode of the diode is connected to the gate a cathode end of the diode for detecting a secondary current of the current transformer, and an anode end of the arrester diode is connected to a negative terminal of the secondary side coil of the current transformer for clamping the current transformer twice Side induced voltage. The driving and holding circuit includes a capacitor and a resistor, the capacitor is connected in parallel with the resistor, and one end of the capacitor and the resistor is connected to the gate of the synchronous rectifying switch, and the other end of the capacitor and the resistor is connected to the The source of the synchronous rectification switch, when the synchronous rectification switch has no gate drive signal, can naturally discharge the gate energy. This capacitor is the input equivalent capacitance of the gate or an external physical capacitor. The turn-off signal detecting circuit includes a capacitor and a resistor connected in series with the resistor, and the capacitor is connected to a positive terminal of the secondary side coil of the voltage transformer, and one end of the resistor is connected to the turn-off switch And the capacitor, and the other end of the resistor is connected to the negative terminal of the primary side coil of the current transformer for detecting the shutdown signal. The turn-off switch is a PNP type transistor, the base of which is connected to the turn-off signal detecting circuit, and the emitter thereof is connected to the gate of the synchronous rectifying switch, and the collector thereof is connected to the source of the synchronous rectifying switch . [Embodiment] Referring to the first figure, a circuit diagram of a synchronous rectifier of the present invention is shown. The synchronous rectifier 100 of the present invention comprises: a current transformer 101, a 201220666 synchronous rectification switch 102, a drive voltage stabilization circuit 1〇3, a drive hold circuit 104, a turn-off signal system circuit 1〇5, and a shutdown switch 106. Wherein the current transformer n 1G1 has a secondary side coil and a secondary side coil, one end of the primary side coil being a drain, and the other end being connected to a source of the synchronous rectifier switch 102, and the secondary side coil The two ends are connected with a demagnetization resistor (R1) to provide the current transformer demagnetization loop, and the positive polarity coil end of the secondary side coil is connected to a vapor side diode (D1). 1
該同步整流開關（Q1 )，為金氧半場效電晶 (MOSFET.)内含本體二極體，該本體二極體亦可於該 同步整流開關之汲極與源極之間外加，而該同步整法^ 關102之源極連接至該電流變壓器1〇1 —次侧線圈= 接至該驅動穩壓電路103和該驅動保持電路ι〇4之 端，且該同步整流開關撤之汲極為叫，而該同步整 流開關102之閘極連接至驅動穩壓電路_ 電路104之正端。 ^他勒保符 該驅動穩壓電路103，包括—二極體 一 稽納二極體（zm)，該驅動穩壓電4103 = 流變壓器101二次侧線圈二端，該二次=接至遠電 串聯-電流偵測二極體（D1)之陽極，該、】、二正極端 體（D1)之陰極同時連接該同步整流開關$測一極 閘極與該穩壓稽納二極體（ZD1)陰極她^ ) 1〇2之 電流變壓器101二次側電流，該稽納二極體用 極連接至該同步整流開關（Q1) 102之源極，2 至該電流變壓器101二次側線圈之負板 逆接 電流變壓器101二次側感應的電壓。 以’’制該 該驅動保持電路104，係由一電阻器（R 電容器（Cl)並聯，-端連接至該同步整流開關⑼一) 201220666 102之閘極，而另一端則連接至該同步整流開關（Ql) 102之源極，當該同步整流開關102無閘極驅動信號能 自然洩放閘極能量，而該電容器（C1)可以為外加之實 體電容器或為該同步整流開關（Q1) 102閘極的輸入等 效電容，因此實際應用時，該電容器（C1)可省略不接。 該關斷信號偵測電路105，係由一電容器（C2) 與一電阻器（R3)串聯，該電容器（C2) —端連接至該 電流變壓器（CT1) 101二次側線圈的正極端，而另一 端連接至該關斷開關（Q2) 106之基極與該電阻器 (R3).，該電阻器（R3) —端與該關斷開關（Q2)集極 共同連接至該同步整流開關（Q1) 102之源極，而該電 阻器（R3)之另一端與該電流變壓器101之一次側線圈 之負極端連接。 該關斷開關106,為PNP電晶體，該關斷開關106 之射極連接至該同步整流開關（Q1) 102之閘極，而該 關斷開關106之集極連接至該同步整流開關（Q1) 102 之源極，該關斷開關106之基極連接至該電容器（C2) 與電阻器（R3)，且該關斷開關106之基極可串接一二 極體（圖未示），以增加該基極與該射極之間的逆向電 壓承受能力。 另外為便於說明本實施例之同步整流器100應用 於各式的轉換器上，可簡化為如第二圖所示之電路圖， 由圖可看出，本發明同步整流器100形成一 P極及N極 接腳之模組，且圖中所示之同步電路（SC)包含第一圖 所示之驅動穩壓電路103、關斷開關106、關斷信號偵 測電路105及驅動保持電路104。 請參考第三圖，係顯示本發明另一實施例之同步 整流器之電路圖。本實施例之同步整流器100,包含： 201220666 一電流變壓器101、一同步整流開關102、一驅動穩壓 電路103、一驅動保持電路104、一關斷信號偵測電路 105及一關斷開關106，其中該電流變壓器101具有一 次側線圈及二次側線圈，該一次側線圈的一端為N極， 而另一端連接至該同步整流開關102之汲極，而該二次 側線圈的二端則連接有一去磁電阻（R1)，以提供該電 流變壓器101去磁回路，且該二次側線圈之正極性線圈 端連接至一電流偵側二極體（D1)。 該同步整流開關（Q1) 102，為金氧半場效電晶 φ 體（ MOSFET)内含本體二極體，而該同步整流開關102 之汲極連接至該電流變壓器101 —次側線圈，而該同步 整流開關102之源極為P極，且該同步整流開關102之 源極連接至該驅動穩壓電路103與該驅動保持電路104 之負端，而該同步整流開關102之閘極連接至驅動穩壓 電路103和驅動保持電路104之正端。 該驅動穩壓電路103,係連接至該電流變壓器101 二次侧線圈二端，該二次側線圈之正極端串聯一電流偵 測二極體（D1)，該電流偵測二極體（D1)之陰極同時 • 連接該同步整流開關（Q1) 102之閘極與該穩壓稽納二 極體（ZD1)陰極端，該稽納二極體（ZD1)陽極連接 至該同步整流開關（Q1) 102之源極。 該驅動保持電路104，係由一電阻器（R2)與一 電容器（C1)並聯，一端連接至該同步整流開關（Q1) 102之閘極，而另一端則連接至該同步整流開關（Q1) 102之源極，而該電容器（C1)可以為該同步整流開關 (Q1) 102之閘極的輸入等效電容，因此實際應用時， 該電容器（C1)可省略不接。 該關斷信號偵測電路105，係由一電容器（C2) 201220666 201220666 該電容器（C2) —端連接至該 一次側線圈的正極端，而另一 與一電阻器（R3)串聯 電流變壓器（CT1 ) 101 $連接至該關斷開關（Q2) 106之基極與該電阻器 R3)，該電阻器（R3) 一端與該關斷開關ι〇6 集極共同連接至該同步整流開關（Q1) 1〇2之源極。 邊關斷開關106,為PNP電晶體，該關斷開關1〇6 之射極連接至該同步整流開關（Q1) 102之閘極，而該 關斷開關106之集極連接至該同步整流開目⑽）1〇2 之源極，該關斷開關106之基極連接至該電容器（c2) 與電阻器（R3)。 另外為便於說明本實施例之同步整流器10〇應用 於各式的轉換器上，可簡化為如第四圖所示之電路圖， 由圖可看出，本發明同步整流器100形成一 P極及^^極 接腳之模組，且圖中所示之同步電路（SC)包含第一圖 所示之驅動穩壓電路103、關斷開關106、關斷信號偵 測電路105及驅動保持電路1〇4。 睛參考第五圖係顯示本發明第一圖實施例應用於 一返馳式轉換器之電路圖。該返驰式轉換器包含一電源 系統107、一返馳式開關電路108、微動開關1〇9、返馳 式變壓器（T1)、本發明之同步整流器1〇〇以及一輸出 端電容（Co) ’其中該電源系統1〇7之正極端係與該返 馳式變壓器108之一次側線圈的負極性端連接，而^電 源系統107之負極端係與該微動開關1〇9之源極連=。 108連接。 該微動開關109，為金氧半場效電晶體 (MOSFET)内含本體二極體，且該微動開關ι〇9"^沒 極係為該返馳式變壓器（T1)之一次侧線圈的正極性端 連接’而該微動開關109之閘極係與該返馳式開關電路 201220666 該返驰式變壓器（τι)之二次側線圈的正極性端 係與本發明之同步整流器100的Ρ極連接，而該輸出端 電容（Co)之二端貝|J分別與本發明之同步整流器100的 N極及該返馳式變壓器（T1)之二次側線圈的負極性端 連接，而該輸出端電容（Co)之一端再連接至一電壓輸 出正極端（+Vout )，而該輸出端電容（Co)之另一端再 連接至一電壓輸出負極端（-Vout)，而形成一可工作於 連續或非連續電流模式之返驰式轉換器。 請參考第六圖係顯示本發明第一圖實施例應用 ϋ 於一返驰式轉換器之另一實施例之電路圖。本實施例之 結構大致同於第五圖之實施例，不同之處在於該返馳式 變壓器（Τ1)之二次側線圈的負極性端係與本發明之同 步整流器100的Ρ極連接，而形成一可工作於連續或非 連續電流模式之返驰式轉換器。 以上為本發明之實施方式，依返驰式轉換器（第 五圖及第六圖）應用為例，其電路的動作原理可以依工 作於連續電流模式（第七圖），與工作於非連續電流模 式（第八圖），加以說明。 參 當本發明應用於連續電流模式時，分別以下列工 作時段加以說明： 一、時段to〜tl，當工作時間位於to時，此時因返驰式 變壓器（T1) 一次侧主開關關閉，二次側線圈將儲存於 變壓器的能量釋放至輸出端，此時因同步整流開關（Q1) 102尚未導通，故初期的電流流經電流變壓器（CT1) 101及同步整流開關（Q1) 102内部的本體二極體，與 輸出端電容（Co)形成迴路，t0至tl之間電流快速的 增加，當時間到達tl電流變壓器101二次側線圈即感應 出一電壓，電流流經二極體（D1)與稽納二極體（ZD1)， 11 201220666 依據法拉第電磁感應定律二次側會產生與一次側圈數 成反比的電流，此時流過稽納二極體（ZD1 )，其電流增 加而達到崩潰電壓Vz，而不致於電壓再上升，此時同時 對於電容器（C1)充電，當同步整流開關（Q1) 102閘 極與源極間達到導通電壓》主電流因Q1導通》電流由 本體二極體轉流過本體内部，因本體二極體先導通使Q1 源極與 >及極間電壓差很低（約1V )’ Q1本體再導通*故 此時段為零電壓切換導通； 二、 時段tl〜t2，此時段因電流變壓器101二次側端的 鲁 電流持續讓稽納二極體（ZD1)於崩潰模式而使電壓保 持於崩潰電壓Vz，同步整流開關（Q1) 102持續保持導 通狀態，當時間於t2時，電流變壓器101二次側端的產 生的感應電壓幾乎與崩潰電壓Vz相同，電流偵測二極 體（D1)已無順向電流，因與電流變壓器101二次側繞 組為同一回路，故此時可以發現二次側繞組電壓幾乎降 至零伏特，由於電容器C2—端順間降至零伏特，而使 同步整流開關102之閘極所保持的電壓順間向電容器 C2充電而使閘極電壓稍為下降，因閘極電壓尚在可以驅 鲁 動同步整流開關102的範圍，故此時同步整流開關102 並未關閉，繼續導通； 三、 時段t2〜t3，此時段因電流變壓器101二次側因無 順向的感應電壓並轉趨於負電壓，二極體（D1)沒有順 向電流，同時於時關斷信號偵測電路105，偵測到電 流變壓器101二次側下降的電壓，而使得Q1閘極電壓 因經由Q2向電容器（C2)充電，其Q1閘極電壓因而 略下降，此時驅動保持電路104繼續維持同步整流開關 12 201220666 102導通的電壓’電流變壓器1〇1 一次側尚有順向電流， 二次側尚未完全反向成重置電壓，故關斷開關未動作而 使同整流開關（Q1)持續保持導通狀態； 四、時段t3〜t4，此時因返驰式變壓器（τΐ)工作於連 續電流模式，t3幾乎等於t4，電流變壓器1〇1 一次側順 向電流瞬間降至零電流，電流變壓器1〇1藉由二次側電 阻器（R1)，產生去磁重置的逆向電壓，當關斷信號偵 測電路105，偵測到電流變壓器1〇1二次側逆向重置電 壓時’使關斷開關（Q2 )106瞬間產生比而使電晶體（Q2 ) 快速導通，將同步整流開關（Q1) 1〇2閘極上的電壓能 快速下降而關斷同步整流開關（Q1) 1〇2，以防止逆電 流產生。 當本發明應用於非連續電流模式時，請參閱第八 圖’分別以下列工作時斷加以說明： 二、巧段to〜tl，當工作時間位於τ〇時，此時因返馳式 麦壓器（T1) 一次側主開關關閉，二次側線圈將儲存於 邊壓器的能置釋放至輸出端，此時因同步整流開關（) 102尚未導通，故初期的電流流經電流變壓器（CT1) 101及同步整流開關（Q1) 102内部的本體丄極體，與 輸出端電容（CG)形成回路，tG至tl之間電流快速的 增加’當時間到達tl電流變壓器101二次側線圈即感應 出電壓，電流流經二極體（D1 )與稽納二極體（)， 依據法拉第電磁感應定律二次側會產生與一次側圈數 成反比的電流，此時流過稽納二極體（ZD1)，其電流增 加而達到崩潰電壓Vz，而不致於電壓再上升，此時同時 13 201220666 對於電容器（Cl)充電，當同步整流開關（Ql) 102之 閘極與源極間達到導通電壓，主電流因Q1導通，電流 由本體二極體轉流過本體内部，因本體二極體先導通使 Q1源極與汲極間電壓差很低（約IV)，Q1本體再導通， 故此時段為零電壓切換導通； 二、 時段tl〜t2，此時段因電流變壓器101二次側端的 電流持續讓稽納二極體（ZD1)於崩潰模式而使電壓保 持於崩潰電壓Vz，同步整流開關（Q1) 102持續保持導 通狀態，當時間於t2時，電流變壓器101 —次側端的電 流已趨近於零電流，電流變壓器101二次側產生重置電 壓，而觸動關斷信號偵測電路105 ; 三、 時段t2〜t3,此時段t2幾乎等於t3,電流變壓器101 一次側端的電流已趨近於零電流，電流變壓器101二次 側產生重置電壓，而觸動關斷信號偵測電路105，因電 流變壓器101 —次側流過的電流為零，電流變壓器101 藉由二次側電阻器（R1)，產生去磁重置的逆向電壓， 當關斷信號偵測電路105，偵測到電流變壓器101二次 側逆向電壓時，關斷開關（Q2) 106瞬間產生lb而使電 晶體（Q2)快速導通，使同步整流開關（Q1) 102閘極 上的電壓能快速下降能快速下降而關斷同步整流開關 (Q1) 102，以防止逆電流產生； 四、 時段t3〜t4，此時因電流變壓器101二次側為負電 壓，變壓器尚在去磁重置階段，因關斷開關（Q2) 106 之基極有一電阻器（R3)，使電晶體（Q2)持續讓同步 整流開關（Q1) 102保持關閉狀態，時間於t4時返馳式 201220666 變壓器（τι) 一次側開關導通，當一次側開關關閉時即 由to再次循環。 綜上所述，本發明之同步整流器可應用於連續或 非連續電流模式，而同步整流器導通時可以先由本體二 極體先導通再使同步整流開關導通，因而降低了切換損 失與導通損失，當電流變壓器一次側無電流流通時能即 時關閉，尤其在非連續電流模式操作時無逆向漏電流產 生，故此發明之同步整流器適合應用於各種電源拓樸中 替代整流二極體的功能，各種電源拓樸電路圖應用範例 如第五圖、第六圖、第九圖、第十圖，第五圖及第六圖 為應用於返馳式轉換器之電路圖，上述已說明，而第九 圖為應用於順向式轉換器之電路圖，此同步整流器可替 換順向整流二極體或飛輪二極體，或二者皆用本發明同 步整流器替換，如圖所示，此為技術領域中具有通常知 識者，由本發明之圖式的揭示均能理解，故在此不再詳 述。而第十圖為本發明應用於全（半）橋式轉換器變壓 器二次侧端之應用電路圖，同樣地，第十圖亦為此技術 領域中具有通常知識者，由本發明之圖式的揭示均能理 解，故在此不再詳述。 15 201220666 【圖式簡單說明】 第一圖係顯示本發明同步整流器之電路圖。 第=圖係顯示本發明同步整流器之簡易電路圖。 第三圖係顯示本發明另一實施例之同步整流器之 電路圖。 第四圖係顯示本發明另—實施例之同步整流器之 間易電路圖。 μ圖係顯林發明第―®之畔整流11應用於 返规式轉換器之電路圖。 返触式圖之同步整流11應用於 式轉換态之另一實施例之電路圖。 第七圖係顯示本發明同步整流器應用於返驰 換裔六且工作於連續電流模式之時序圖。 第人圖_示本發明同步紐輯用驰 換益上且工作於非連續電流模式之時序圖。 換器㈣㈣順向式轉 橋式應㈣全（半^ 、益i堅器一次側端之應用電路圖。 之電路第®1V"圖係顯示習知的電流變壓驅動同步整流器 知技蚊—制錄流返驰式 【主要元件符號說明】 1〇0同步整流器 ίο 1 一_電流變壓器 1()2”_同步整流開關 103 驅動穩壓電路 201220666 104 - 105 - 106 - 107 - 108 -109 - 驅動保持電路 關斷信號偵測電路 關斷開關 電源糸統 返驰式開關電路 微動開關 17The synchronous rectification switch (Q1) is a metal oxide half field effect transistor (MOSFET) having a body diode, and the body diode can also be applied between the drain and the source of the synchronous rectification switch, and the The source of the synchronous whole method ^ 102 is connected to the current transformer 1〇1 - the secondary side coil = the end connected to the driving regulator circuit 103 and the drive holding circuit ι4, and the synchronous rectification switch is extremely removed The gate of the synchronous rectification switch 102 is connected to the positive terminal of the driving regulator circuit_circuit 104. ^他保符 The drive voltage regulator circuit 103, including - diode-generative diode (zm), the drive voltage regulator 4103 = flow transformer 101 secondary side coil two ends, the second = connected to The anode of the remote power series-current detecting diode (D1), the cathode of the second positive terminal body (D1) is simultaneously connected to the synchronous rectifier switch, and the one-pole gate and the voltage-stabilizing diode are connected. (ZD1) Cathode her ^) 1〇2 current transformer 101 secondary side current, the Genen diode is connected to the source of the synchronous rectification switch (Q1) 102, 2 to the secondary side of the current transformer 101 The negative plate of the coil is reversed to the voltage induced by the secondary side of the current transformer 101. The driving and holding circuit 104 is made of a resistor (the parallel connection of the R capacitor (Cl), the - terminal is connected to the synchronous rectifying switch (9)), and the other end is connected to the synchronous rectification. The source of the switch (Q1) 102, when the synchronous rectification switch 102 has no gate drive signal, can naturally discharge the gate energy, and the capacitor (C1) can be an external physical capacitor or the synchronous rectification switch (Q1) 102. The input capacitance of the gate is equivalent, so in practical applications, the capacitor (C1) can be omitted. The turn-off signal detecting circuit 105 is connected in series by a capacitor (C2) and a resistor (R3) connected to the positive terminal of the secondary side coil of the current transformer (CT1) 101, and The other end is connected to the base of the shutdown switch (Q2) 106 and the resistor (R3). The resistor (R3) terminal and the shutdown switch (Q2) are collectively connected to the synchronous rectifier switch ( Q1) The source of 102, and the other end of the resistor (R3) is connected to the negative terminal of the primary side coil of the current transformer 101. The turn-off switch 106 is a PNP transistor, the emitter of the turn-off switch 106 is connected to the gate of the synchronous rectification switch (Q1) 102, and the collector of the turn-off switch 106 is connected to the synchronous rectification switch (Q1) a source of 102, the base of the shutdown switch 106 is connected to the capacitor (C2) and the resistor (R3), and the base of the shutdown switch 106 can be connected in series with a diode (not shown). To increase the reverse voltage withstand capability between the base and the emitter. In addition, for convenience of description, the synchronous rectifier 100 of the present embodiment can be applied to various types of converters, which can be simplified as a circuit diagram as shown in the second figure. As can be seen from the figure, the synchronous rectifier 100 of the present invention forms a P pole and an N pole. The module of the pin, and the synchronous circuit (SC) shown in the figure includes the driving regulator circuit 103, the shutdown switch 106, the shutdown signal detecting circuit 105, and the driving and holding circuit 104 shown in the first figure. Referring to the third figure, there is shown a circuit diagram of a synchronous rectifier according to another embodiment of the present invention. The synchronous rectifier 100 of the embodiment includes: 201220666 a current transformer 101, a synchronous rectification switch 102, a drive voltage stabilization circuit 103, a drive holding circuit 104, a shutdown signal detection circuit 105, and a shutdown switch 106. The current transformer 101 has a primary side coil and an secondary side coil. One end of the primary side coil is an N pole, and the other end is connected to the drain of the synchronous rectification switch 102, and the two ends of the secondary side coil are connected. There is a demagnetization resistor (R1) to provide the current transformer 101 demagnetization loop, and the positive polarity coil end of the secondary side coil is connected to a current sense diode (D1). The synchronous rectification switch (Q1) 102 is a metal oxide half field effect transistor (MOSFET) containing a body diode, and the drain of the synchronous rectification switch 102 is connected to the current transformer 101 - the secondary side coil, and the The source of the synchronous rectification switch 102 is extremely P pole, and the source of the synchronous rectification switch 102 is connected to the negative terminal of the driving regulator circuit 103 and the driving and holding circuit 104, and the gate of the synchronous rectification switch 102 is connected to the driving terminal. The positive terminal of the voltage circuit 103 and the drive holding circuit 104. The driving regulator circuit 103 is connected to the secondary side coil of the current transformer 101, and the positive terminal of the secondary side coil is connected in series with a current detecting diode (D1), and the current detecting diode (D1) The cathode is simultaneously connected to the gate of the synchronous rectification switch (Q1) 102 and the cathode end of the Zener diode (ZD1), and the anode of the Zener diode (ZD1) is connected to the synchronous rectification switch (Q1) ) The source of 102. The drive holding circuit 104 is connected in parallel with a capacitor (C1) by a resistor (R2), one end is connected to the gate of the synchronous rectification switch (Q1) 102, and the other end is connected to the synchronous rectification switch (Q1). The source of 102, and the capacitor (C1) can be the input equivalent capacitance of the gate of the synchronous rectification switch (Q1) 102, so in practical applications, the capacitor (C1) can be omitted. The turn-off signal detecting circuit 105 is composed of a capacitor (C2) 201220666 201220666. The capacitor (C2) is connected to the positive terminal of the primary side coil, and the other is connected to a resistor (R3) in series with the current transformer (CT1). 101 $ is connected to the base of the shutdown switch (Q2) 106 and the resistor R3), and one end of the resistor (R3) is connected to the shutdown switch ι6 to the synchronous rectifier switch (Q1) The source of 1〇2. The edge turn-off switch 106 is a PNP transistor, the emitter of the turn-off switch 1〇6 is connected to the gate of the synchronous rectification switch (Q1) 102, and the collector of the turn-off switch 106 is connected to the synchronous rectification head. (10)) The source of 1〇2, the base of which is connected to the capacitor (c2) and the resistor (R3). In addition, for convenience of explanation, the synchronous rectifier 10 of the present embodiment is applied to various converters, which can be simplified as a circuit diagram as shown in the fourth figure. As can be seen from the figure, the synchronous rectifier 100 of the present invention forms a P pole and ^ The pole-connected module, and the synchronous circuit (SC) shown in the figure includes the driving regulator circuit 103, the shutdown switch 106, the shutdown signal detecting circuit 105, and the drive holding circuit 1 shown in the first figure. 4. The fifth embodiment shows a circuit diagram of a first embodiment of the present invention applied to a flyback converter. The flyback converter includes a power system 107, a flyback switch circuit 108, a micro switch 1〇9, a flyback transformer (T1), a synchronous rectifier 1〇〇 of the present invention, and an output capacitor (Co). Wherein the positive terminal of the power system 1〇7 is connected to the negative terminal of the primary side coil of the flyback transformer 108, and the negative terminal of the power supply system 107 is connected to the source of the microswitch 1〇9. . 108 connections. The micro switch 109 is a metal oxide half field effect transistor (MOSFET) containing a body diode, and the micro switch ι〇9"^ is the positive polarity of the primary side coil of the flyback transformer (T1) The terminal is connected to the gate of the micro switch 109 and the flyback switch circuit 201220666. The positive terminal of the secondary side coil of the flyback transformer (τι) is connected to the drain of the synchronous rectifier 100 of the present invention. The two terminals of the output capacitor (Co) are respectively connected to the N pole of the synchronous rectifier 100 of the present invention and the negative terminal of the secondary side coil of the flyback transformer (T1), and the output capacitor One end of (Co) is connected to a voltage output positive terminal (+Vout), and the other end of the output capacitor (Co) is connected to a voltage output negative terminal (-Vout) to form a continuous or A flyback converter in discontinuous current mode. Please refer to the sixth figure for a circuit diagram showing another embodiment of the first embodiment of the present invention applied to a flyback converter. The structure of this embodiment is substantially the same as that of the fifth embodiment, except that the negative polarity end of the secondary side coil of the flyback transformer (Τ1) is connected to the drain of the synchronous rectifier 100 of the present invention. A flyback converter that operates in a continuous or discontinuous current mode is formed. The above is an embodiment of the present invention. According to the application of the flyback converter (fifth and sixth figures), the operation principle of the circuit can be operated according to the continuous current mode (seventh figure), and the operation is discontinuous. Current mode (eighth figure), to be explained. When the present invention is applied to the continuous current mode, the following working periods are respectively described: 1. Time period to~tl, when the working time is at to, at this time, the primary side switch of the flyback transformer (T1) is turned off, The secondary coil discharges the energy stored in the transformer to the output terminal. At this time, since the synchronous rectifier switch (Q1) 102 is not turned on, the initial current flows through the body of the current transformer (CT1) 101 and the synchronous rectifier switch (Q1) 102. The diode forms a loop with the output capacitor (Co). The current between t0 and t1 increases rapidly. When the time reaches tl, the secondary side coil of the current transformer 101 induces a voltage, and the current flows through the diode (D1). With the Jenus diode (ZD1), 11 201220666 According to the Faraday's law of electromagnetic induction, the secondary side will produce a current that is inversely proportional to the number of primary turns. At this time, the current is passed through the Zener diode (ZD1), and its current increases and collapses. Voltage Vz, so that the voltage does not rise again. At this time, the capacitor (C1) is charged. When the synchronous rectification switch (Q1) 102 reaches the conduction voltage between the gate and the source, the main current is turned on by Q1. The body diode is diverted through the inside of the body, because the body diode is first turned on, so that the voltage difference between the Q1 source and the > and the pole is very low (about 1V) 'Q1 body re-conducting*, so the zero voltage switch is turned on during this period; Time period t1~t2, during which the synchronous current rectification switch (Q1) 102 is continuously turned on because the Lu current of the secondary side end of the current transformer 101 continues to cause the voltage of the Zener diode (ZD1) to be in the collapse mode to maintain the voltage at the breakdown voltage Vz. State, when time is t2, the induced voltage generated at the secondary side of the current transformer 101 is almost the same as the breakdown voltage Vz, and the current detecting diode (D1) has no forward current due to the secondary winding of the current transformer 101. For the same loop, it can be found that the secondary winding voltage drops to zero volts at this time, and the voltage held by the gate of the synchronous rectifier switch 102 is charged to the capacitor C2 as the capacitor C2 terminal drops to zero volts. And the gate voltage is slightly decreased, because the gate voltage is still able to drive the range of the synchronous rectification switch 102, so the synchronous rectification switch 102 is not turned off at this time, and continues to conduct; 3. Time period t2~ T3, during this period, because the secondary side of the current transformer 101 has no forward induced voltage and tends to a negative voltage, the diode (D1) has no forward current, and at the same time, the signal detecting circuit 105 is turned off, detecting The voltage of the secondary side of the current transformer 101 is lowered, so that the Q1 gate voltage is charged to the capacitor (C2) via Q2, and the Q1 gate voltage thereof is thus slightly decreased. At this time, the drive holding circuit 104 continues to maintain the synchronous rectification switch 12 201220666 102. The voltage 'current transformer 1〇1 has a forward current on the primary side, and the secondary side has not completely reversed into the reset voltage, so the shutdown switch does not operate and the same rectifier switch (Q1) remains in the on state; T3~t4, at this time, because the flyback transformer (τΐ) works in the continuous current mode, t3 is almost equal to t4, and the current transformer 1〇1 primary side forward current instantaneously drops to zero current, and the current transformer 1〇1 is used twice. The side resistor (R1) generates a reverse voltage for the demagnetization reset. When the signal detection circuit 105 is turned off, the current transformer 1〇1 secondary side reverse reset voltage is detected, 'the shutdown switch (Q2) 106 is turned off. Instantaneous ratio That the transistor (Q2) is turned on quickly, the voltage across the synchronous rectifier switch (Q1) 1〇2 rapid drop in the gate off the synchronous rectification switch (Q1) 1〇2 to prevent reverse current generated. When the present invention is applied to the discontinuous current mode, please refer to the eighth figure's description of the following working breaks respectively: 2. The segment to~tl, when the working time is at τ〇, at this time, due to the flyback type wheat pressure (T1) The primary side main switch is turned off, and the secondary side coil discharges the energy stored in the voltage regulator to the output terminal. At this time, since the synchronous rectification switch () 102 is not turned on, the initial current flows through the current transformer (CT1). 101 and the synchronous rectifier switch (Q1) 102 internal body drain body, and the output terminal capacitance (CG) forms a loop, the current between tG and t1 increases rapidly 'when time reaches tl current transformer 101 secondary side coil is induction The voltage is output, and the current flows through the diode (D1) and the second diode (). According to the Faraday's law of electromagnetic induction, a secondary current is generated in inverse proportion to the number of primary turns, and the current is passed through the Zener diode ( ZD1), its current increases to reach the breakdown voltage Vz, and the voltage does not rise again. At this time, 13 201220666 charges the capacitor (Cl), and when the gate of the synchronous rectification switch (Q1) 102 reaches the conduction voltage, Main current Q1 is turned on, and the current is diverted from the body diode through the body. Because the body diode is turned on first, the voltage difference between the source and the drain of Q1 is very low (about IV), and the Q1 body is turned on again. Therefore, the voltage is switched to zero during this period. 2. The second period is t1 to t2. During this period, the current of the secondary side of the current transformer 101 continues to cause the voltage of the Zener diode (ZD1) to remain at the collapse voltage Vz, and the synchronous rectifier switch (Q1) 102 continues. Maintaining the on state, when the time is t2, the current of the secondary side of the current transformer 101 has approached zero current, and the secondary side of the current transformer 101 generates a reset voltage, and the off signal detection circuit 105 is activated; 3. Time period t2 〜t3, this period t2 is almost equal to t3, the current of the primary side of the current transformer 101 has approached zero current, the secondary side of the current transformer 101 generates a reset voltage, and the off signal detection circuit 105 is activated, because the current transformer 101 is The current flowing through the secondary side is zero, and the current transformer 101 generates a reverse voltage of the demagnetization reset by the secondary side resistor (R1). When the signal detecting circuit 105 is turned off, the current transformer 101 is detected twice. In the reverse voltage, the shutdown switch (Q2) 106 instantaneously generates lb to make the transistor (Q2) turn on quickly, so that the voltage on the gate of the synchronous rectifier switch (Q1) 102 can be rapidly decreased, and the synchronous rectifier switch can be turned off (Q1). 102, to prevent reverse current generation; Fourth, the period t3 ~ t4, at this time because the secondary side of the current transformer 101 is a negative voltage, the transformer is still in the demagnetization reset phase, because the base of the shutdown switch (Q2) 106 has Resistor (R3), so that the transistor (Q2) keeps the synchronous rectification switch (Q1) 102 off, and the time is reversed at t4. 201220666 Transformer (τι) The primary side switch is turned on, when the primary side switch is turned off, To cycle again. In summary, the synchronous rectifier of the present invention can be applied to a continuous or discontinuous current mode, and the synchronous rectifier can be turned on first by the body diode and then the synchronous rectifier switch is turned on, thereby reducing switching loss and conduction loss. When the current transformer has no current flowing on the primary side, it can be turned off immediately, especially in the non-continuous current mode operation, and no reverse leakage current is generated. Therefore, the synchronous rectifier of the invention is suitable for the function of replacing the rectifier diode in various power supply topologies, and various power sources. The topographical circuit application examples are, for example, fifth, sixth, ninth, tenth, fifth, and sixth figures, which are circuit diagrams applied to a flyback converter, which have been described above, and the ninth figure is an application. In the circuit diagram of the forward converter, the synchronous rectifier can replace the forward rectifying diode or the flywheel diode, or both are replaced by the synchronous rectifier of the present invention, as shown in the figure, which is a common knowledge in the technical field. The disclosure of the drawings of the present invention can be understood, and therefore will not be described in detail herein. The tenth figure is an application circuit diagram of the secondary side of the transformer applied to the full (semi) bridge converter. Similarly, the tenth figure is also known to those skilled in the art, and the disclosure of the invention is disclosed. Can understand, so it will not be detailed here. 15 201220666 [Simple Description of the Drawings] The first figure shows the circuit diagram of the synchronous rectifier of the present invention. Fig. = is a simplified circuit diagram showing the synchronous rectifier of the present invention. The third figure is a circuit diagram showing a synchronous rectifier of another embodiment of the present invention. The fourth figure shows an easy circuit diagram of a synchronous rectifier of another embodiment of the present invention. The μ map is shown in the circuit diagram of the return-to-regulator. The synchronous rectification 11 of the back touch pattern is applied to the circuit diagram of another embodiment of the switching state. The seventh figure shows the timing diagram of the synchronous rectifier of the present invention applied to the flyback and operating in the continuous current mode. The first figure shows the timing diagram of the synchronization key of the present invention which is used in the non-continuous current mode. Converter (4) (4) Forward-type bridge type should be (4) full (half-^, Yi-i-en equipment first-side application circuit diagram. Circuit 1/1V" diagram shows the conventional current transformer-driven synchronous rectifier known as mosquito-based Streaming and returning type [Main component symbol description] 1〇0 synchronous rectifier ίο 1 _ current transformer 1 () 2" _ synchronous rectifier switch 103 driving voltage regulator circuit 201220666 104 - 105 - 106 - 107 - 108 -109 - Driver Keep circuit shutdown signal detection circuit to turn off switching power supply 糸 system flyback switch circuit micro switch 17