200820572 九、發明說明： 【發明所屬之技術領域】 本發明涉及一種識別電源適配器之控制電路與方法， 尤係涉及一種可識別插接於電子產品之電源適配器是否匹 配之控制電路及其識別方法。 【先前技術】 各類電子產品，例如筆記本電腦（Notebook C〇mpUter)、桌上型電腦（Desktop Computer)和電視 _ (Television)在使料均需要錢電做為電子產品之電 源。常用的一種交流電源適配器（ACadapi〇r)可將一般交 流市電轉換成電子產品所需之直流電，以提供電子產品所 需電源，同時現代各種電子產品如移動電話（Μ〇· telephone)個人數位助理（pers〇nai 邮制 assis攸，pda)、 數位靜態/動態相機（digital stiii/dynamic camera)，在為使 用之電池進行充電時，也需要搭配電源適配器使用。如5 , 所示，t知電源適配器其内部結構一般包括降壓電路和 整流電路20兩大部分，將經降壓與整流之低壓直流電輸入 至電子產品，使其工作，該電源適配器具有兩個輸出端， 即正極輸出端1和負極輸出端2。 近年來，以筆記型電腦為例，由於電腦技術之突飛猛 進’也使得中央處理單元（cpu)與視頻圖形陣列（vide〇 Graphics Array，VGA)之效能得以不斷提升，此外各種新功 能之加入，則促使筆記型電腦對電功率之需求也相對地增 加。目前在市場上，有些電源適配器之不法製造商為了追 7 200820572 、、/門擅自饭昼品牌、冒用包裝、以次充好等非法手段 擾乱市豕秩序，由此可知目前市面上電源適配器類型之多 樣化與複雜程度。 口電源適配n麵之錄倾複雜，很容終致電子 產品與不她配之電·配器_，從而影㈣子產品之 糸統歡性與安全錄，若使產品餅駐作在非正常之 =作狀4下，電子產品之制壽命也會大大縮短。而且以BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit and method for identifying a power adapter, and more particularly to a control circuit and a method for identifying whether a power adapter plugged into an electronic product matches. [Prior Art] Various types of electronic products, such as notebook computers (Notebook C〇mpUter), desktop computers (Desktop Computer), and televisions (Television), require electricity as a power source for electronic products. A commonly used AC power adapter (ACadapi〇r) converts general AC mains into DC power required for electronic products to provide power for electronic products, as well as modern electronic products such as mobile phones (Μ〇·电话) personal digital assistants. (Pers〇nai postal ass攸, pda), digital static/dynamic camera (digital stiii/dynamic camera), also need to be used with the power adapter when charging the battery used. As shown in FIG. 5, the internal structure of the power adapter generally includes two steps of a step-down circuit and a rectifier circuit 20, and the low-voltage DC power that is stepped down and rectified is input to the electronic product to operate, and the power adapter has two The output terminals are the positive output terminal 1 and the negative output terminal 2. In recent years, taking notebook computers as an example, the rapid advancement of computer technology has also led to the continuous improvement of the performance of central processing units (Cpu) and video graphics arrays (VIDE), and the addition of new features. The demand for electric power in notebook computers has also increased relatively. At present, some unscrupulous manufacturers of power adapters in order to chase 7 200820572, / / door unauthorized rice cooker brand, fraudulent use of packaging, shoddy and other illegal means to disrupt the order of the market, thus know the current type of power adapter on the market Diversification and complexity. The port power supply adapts to the n-face recording, which is very complicated, and the end result is that the electronic product is not equipped with the electric/distributor _, so that the shadow of the (four) sub-products is recorded and safely recorded. In the case of 4, the life of electronic products will be greatly shortened. And
充好假目un牌之不正當市場行為，嚴重侵害原電子產品 及正規電源適配器製造商之利益。 因此’若電子產品之系統端可以識 ，之類型的話，電子產品之使用者則可以免於用= 適配器而造成損害電子產品，同 ’、 場秩序。 i 叫’也可以更好地維護市 【發明内容】 有雲於此，有必要提俾_ ^ 路與方法。蛛供種朗電源適配器之控制電 一種識別電源適配器之控制電路，包括—適配 糸統端，該適配㈣包括將高電壓降為低電壓之— =和將交流電轉換為直流電之—整流電路，該適配 、有正極輸出端與負極輸㈣，該正極輸出端上連接^ 分壓電路’該祕端包括-_電路，該正 關電路連接，該分壓電路設有一控制輸出端，該控^ 端與開關電路連接以控制該開關電路之開啟盘關閉輪出 一種識別電源適配器之方法，々I 〜 包括如下步驟：通過— 8 200820572 職電_輸人至電源雜器之高數流電轉換成低壓直 流電’ ϋ將該低壓直流電接入至一開關電路中；將該低壓 直流電分壓以形成一控制電壓；將該控制電壓輸入至上述 開關電路，以控制該開關電路之開啟與關閉。 與習知技術相比，通過增加一控制輸出端及一開關電 路’並利用該控制輸出端實現對該開關電路之控制，以識 別所使用之電源適配器與電子產品是否相匹配，使市場習 知之各類假冒之電源適配器無法實現正常供電，達到拒絕 攀假冒產品之目的。 【實施方式】 下面參照附圖，結合實施例作進一步說明。 本發明提供—種識職源適配器之控魏路與方法， 圖1是本發明識別電源適配器之控制電路之電路功能方塊 圖、’該控愼路可制於筆記本電腦、桌上型電腦、手機、 電視機或其他電子產品’包括—適配器端i5Q和一系統端 100。 Φ 該適配器端15〇包括降壓電路1〇、整流電路2〇及分 壓電路30，系統端100包括與適配器端15〇連接之開關電 ，4〇及接文供電之系統5〇。由於電力網提供給用戶的是 1¾壓交流電’而各種電子產品一般需要用低壓直流電，因 而適配器端150把電力網所提供之高壓交流電降壓、整流 轉換成所需要之低壓直流電以供給系統端1〇〇。適配器端 15〇之降壓電路1〇把高壓交流電降為低電壓，整流電路2〇 把經降壓之低壓交流電轉換為大小和方向穩定之低壓直流 9 200820572 . 電，稱㈣路和綠魏20組祕換魏且均採用 習知設計，在此不作贅述。 _用 .適配器端150除了具有常規之電壓輪出端1盘電壓輸 出端2之外，還設置有控制輪出端3，該電壓輪出端工為 來自整流電路20之正極端，該電壓輸出端2為來自整流電 路20之負極端’該控制輸出端3來自分壓電路％，用: 控制開關電路40之開朗。分壓 3〇終流後之低壓 直流電’即將適配器端15〇之電壓輸出端1之輸出電壓， 分成第-電壓和第二電壓兩個不同值之輸出賴，詳如後 述。該電壓輸出端1和控制輪出端3再連接至系統端· 之開關電路40。若該適配器端15〇通過電壓輸出端ι和控 制輸出端3使關電路4叫通，則適配器端⑽之電壓ς 出端1與系統端100連通形成供電通路向連接在開關電路 40上之系統50供電，否則開關電路4〇處於斷開狀離，適 配器端i50之輕輸出端工與系統5〇間之連接為開路，使 • 得系統5〇無法獲得供電，以此判斷所使用之電源適配器與 電子產品是否匹配，其中，該系統5〇可為如上所述之各類 電子產品如筆記本電腦、電視機等。 圖2是本發明一實施例中識別電源適配器之 之電路圖，分壓電路30是由兩個不同阻值之分壓^阻ri、 R2串聯連接在電壓輸出端i和地極（GND)之間形成之串 聯回路’控制輸出端3接在電阻R1和R2之間，根據串聯 電路之分壓特性，控制輸出端3之輸出電壓大小為 兩端分配之麵大小，電壓輸出端i之輸出電壓大小為電 200820572 I^Rl和R2兩端分配之電壓之總和，即電壓輸出端1之輸 出電壓與控概_ 3之細賴之比鮮於電阻ri和 =2之U口與電阻R2之比值。當電源適配器插接在電子產 而上向系㈣1GG供電時’分壓電路3()與關電路⑽通 過電壓輸出端1和控制輸出端3電連接，控制輸出端3之 輸出電壓即是開關電路4()所需之開啟電壓，電壓輪出端工 之輸出電壓即疋電子產品所需之供電電壓，因此，電阻幻 鲁 和R2之總和與電卩1R2之比值應不大於電子產品所需供電 電壓與開關電路40所需開啟電壓之比值，從而可以確^在 不同實施例中分壓電阻R1和R2之大小。 該開關電路40由金屬_氧化物-半導體場效應管 (Meial-Oxide^Semiconductor Field Effect Transistor ^ MOSFET，簡稱MOS場效應管）Q1、q2和電阻R3連接 組成。其中Q2之栅極g與適配器端15〇之控制輸出端3 相連’源極S接地，漏極d與Qi之柵極G相連，之源 • 極S與適配器端150之電壓輸出端i相連，漏極D則連接 至系統50,電阻R3連接在Q1之源極s和q2之漏極D(以 之柵極G)之間。Q2為正電壓導通之N溝道增強型肘〇8 場效應管，在外加栅極G、源極S之間電壓等於或大於Q2 之閥值電壓（VT)時’ Q2導通。Q1為負電壓導通之p溝 道增強型MOS場效應管，其與N溝道增強型m〇S場效應 管之區別在於’ Q1之閥值電壓為負數，當外加柵極G與源 極S之間之電壓為負電壓且絕對值大於其閥值電壓之絕對 值時，Q1才會導通，本實施例中，假定其絕對值與〇2之 11 200820572 閥值電壓相等。 適配器端150通過電壓輸出端1向系統端1〇〇提供電 子產品所需要之低壓直流電，以下以一筆記本電腦作為系 統50之實例作介紹，假設該筆記本電腦所需電壓為18V直 流電，即該適配器端150之電壓輸出端i之輸出電壓應為 18V。開關電路40中Q2為正電壓導通之增強型M〇s場 政應官’假设Q2之閥值電壓為4V，因而Q2之外加栅極g • 〜源、極S間之電壓’即控制輸出端3之輸出電壓需不小於 4V’才能將開關電路4〇打開，根據分壓電路3〇中電阻幻 和R2比值與輸出電壓比值之關係，從而確定分壓電路 中分壓電阻R1可為75K (千歐），R2為25K (千歐），使 得控制輸出端3上之輸出電壓為4·5ν。由於控制輸出端3 之輸出電壓大於q2之閥值電壓，Q2導通，Q2之漏極D 與源極S之間形成通路。由於Q2之源極S接地，Q2之漏 極D與源極S兩極均變為低電平，從而Q1之外加柵極〇 _ 與源極S間之電壓為R3兩端之電壓為—術，其絕對值大 於Q1之閥值電壓，Q1亦導通，Q1之漏極D與源極S之 ^形成通路，適配器端150之電壓輸出端1可向筆記本電 月自^系、、先50供電。若該電源適配器不是相匹配的，由於無 刀壓電路30獲得合適之分壓值，沒有輪出電壓大於Q2之 闕值電壓之控制輪出端3，Q2不導通，即Q2視為斷開， 由於Q1為負電壓導通之P溝道增強型MOS場效應管，q2 斷開之情况下，無電流通過R3，即Q1之栅極〇、源極S 間之電壓為零，所以Q1亦不導通，因而，適配器端150 12 200820572 之，ί出端1無法向筆記本電腦供電。 ” Ή之電源適配器相比較，本發明之系統端100增 兩個作為開關之M0S場效應管Q1、Q2和-個電阻 R3形成之開關電路4〇，適配器端·增加了 一個由兩個電 、酋、寺=串聯形成之分星電路3〇以控制該開關電路40 k <而觸賴之電_配器是錢電子產品相匹 日制電路簡單，增加之電子元件少且成本低廉。由It is a serious violation of the interests of the original electronic products and the manufacturers of regular power adapters. Therefore, if the system side of the electronic product can be recognized, the user of the electronic product can be free from the use of the = adapter to cause damage to the electronic product, the same as the field order. i called ' can also better maintain the city [invention content] There is a cloud here, it is necessary to improve the _ ^ road and method. Controlling circuit of a spider power supply adapter, a control circuit for identifying a power adapter, including - adapting the system, the adaptation (4) includes reducing the high voltage to a low voltage - = and converting the alternating current into a direct current - the rectifier circuit The adaptor has a positive output terminal and a negative input (four), and the positive output terminal is connected to a voltage dividing circuit. The secret terminal includes a -_ circuit, the positive closed circuit is connected, and the voltage dividing circuit is provided with a control output end. The control terminal is connected to the switch circuit to control the open circuit of the switch circuit to turn off a method for identifying the power adapter, and 々I 〜 includes the following steps: through - 8 200820572 vocational power _ input to the high number of power miscellaneous devices The galvanic power is converted into a low-voltage direct current ' ϋ the low-voltage direct current is connected to a switching circuit; the low-voltage direct current is divided to form a control voltage; the control voltage is input to the switching circuit to control the opening of the switching circuit shut down. Compared with the prior art, by adding a control output and a switching circuit 'and using the control output to control the switching circuit to identify whether the power adapter used and the electronic product match, the market is known All kinds of counterfeit power adapters can not achieve normal power supply, and achieve the purpose of refusing to climb counterfeit products. [Embodiment] Hereinafter, the embodiments will be further described with reference to the accompanying drawings. The invention provides a control system and a method for identifying a source adapter. FIG. 1 is a circuit diagram of a circuit for identifying a control circuit of a power adapter according to the present invention, and the control circuit can be implemented in a notebook computer, a desktop computer, or a mobile phone. , TV or other electronic products 'includes - adapter end i5Q and a system end 100. Φ The adapter terminal 15 includes a step-down circuit 1〇, a rectifier circuit 2〇, and a voltage dividing circuit 30. The system terminal 100 includes a switching power connected to the adapter terminal 15〇, and a system for supplying power to the device 5〇. Since the power grid provides the user with 13⁄4 voltage alternating current' and various electronic products generally need low voltage direct current, the adapter terminal 150 steps down and rectifies the high voltage alternating current provided by the power grid into the required low voltage direct current to supply the system end. . The step-down circuit of the adapter terminal 15〇 reduces the high-voltage alternating current to a low voltage, and the rectifier circuit 2 converts the step-down low-voltage alternating current into a low-voltage DC with a stable size and direction. 200820572 . Electric, called (four) road and green Wei 20 The group secrets Wei and both adopt the conventional design, and will not be described here. In addition to the conventional voltage wheel output terminal 1 voltage output terminal 2, the adapter terminal 150 is also provided with a control wheel output terminal 3, the voltage wheel output terminal is from the positive terminal of the rectifier circuit 20, the voltage output The terminal 2 is from the negative terminal of the rectifier circuit 20. The control output terminal 3 is from the voltage dividing circuit %, and is used to: control the cheerfulness of the switching circuit 40. The partial voltage is 3〇, and the low-voltage DC power after the final flow is the output voltage of the voltage output terminal 1 of the adapter terminal 15〇, which is divided into two different values of the first voltage and the second voltage, as will be described later. The voltage output terminal 1 and the control wheel output terminal 3 are connected to the switching circuit 40 of the system terminal. If the adapter terminal 15 turns the circuit 4 through the voltage output terminal ι and the control output terminal 3, the voltage output terminal 1 of the adapter terminal (10) communicates with the system terminal 100 to form a power supply path to the system connected to the switch circuit 40. 50 power supply, otherwise the switch circuit 4〇 is disconnected, the connection between the light output end of the adapter end i50 and the system 5〇 is open circuit, so that the system 5〇 cannot obtain power supply, so as to judge the power adapter used. Whether it matches the electronic product, wherein the system 5 can be various types of electronic products such as a notebook computer, a television set and the like as described above. 2 is a circuit diagram of identifying a power adapter according to an embodiment of the present invention. The voltage dividing circuit 30 is connected in series by a voltage divider ri, R2 of two different resistance values at a voltage output terminal i and a ground electrode (GND). The series circuit formed between the control output terminal 3 is connected between the resistors R1 and R2. According to the voltage dividing characteristic of the series circuit, the output voltage of the output terminal 3 is controlled to be the size of the surface of the two ends, and the output voltage of the voltage output terminal i The size is the sum of the voltages distributed by the two terminals of the 200820572 I^Rl and R2, that is, the ratio of the output voltage of the voltage output terminal 1 to the control _3 is less than the ratio of the U port of the resistors ri and =2 to the resistance R2. When the power adapter is plugged into the electronic product and supplied to the system (4) 1GG, the voltage dividing circuit 3 () and the circuit (10) are electrically connected through the voltage output terminal 1 and the control output terminal 3, and the output voltage of the control output terminal 3 is the switch. The turn-on voltage required for circuit 4 (), the output voltage of the output terminal of the voltage wheel is the power supply voltage required for the electronic product. Therefore, the ratio of the sum of the resistors and the R2 to the voltage of the battery 1R2 should not be greater than that required by the electronic product. The ratio of the supply voltage to the desired turn-on voltage of the switching circuit 40 allows the size of the voltage dividing resistors R1 and R2 to be varied in different embodiments. The switch circuit 40 is composed of a metal-oxide-semiconductor field effect transistor (Meial-Oxide^Semiconductor Field Effect Transistor MOSFET) Q1, q2 and a resistor R3. The gate g of Q2 is connected to the control output terminal 3 of the adapter terminal 15'. The source S is grounded, the drain d is connected to the gate G of the Qi, and the source S is connected to the voltage output terminal i of the adapter terminal 150. The drain D is connected to the system 50, and the resistor R3 is connected between the source s of Q1 and the drain D of Q2 (with gate G). Q2 is a positive-voltage-conducting N-channel enhancement type elbow 8 field effect transistor. When the voltage between the gate G and the source S is equal to or greater than the threshold voltage (VT) of Q2, Q2 is turned on. Q1 is a negative-voltage-conducting p-channel enhancement type MOS field effect transistor, which differs from the N-channel enhancement type m〇S field effect transistor in that the threshold voltage of Q1 is negative, when the gate G and the source S are applied. When the voltage between them is a negative voltage and the absolute value is greater than the absolute value of the threshold voltage, Q1 is turned on. In this embodiment, the absolute value is assumed to be equal to the threshold value of 20082 of 11 200820572. The adapter terminal 150 provides the low voltage DC power required by the electronic product to the system terminal 1 through the voltage output terminal 1. The following is an example of the system 50 as a notebook computer. It is assumed that the voltage required for the notebook computer is 18V DC, that is, the adapter. The output voltage of the voltage output terminal i of the terminal 150 should be 18V. In the switching circuit 40, Q2 is a positive voltage-conducting enhanced M〇s field administrator's assumption that the threshold voltage of Q2 is 4V, so Q2 is added with the gate g • the voltage between the source and the pole S', that is, the control output The output voltage of 3 needs to be no less than 4V' to turn on the switching circuit 4〇. According to the relationship between the resistance illusion and the R2 ratio of the voltage dividing circuit 3〇 and the output voltage ratio, it is determined that the voltage dividing resistor R1 in the voltage dividing circuit can be 75K (thousand ohms), R2 is 25K (thousand ohms), so that the output voltage on the control output 3 is 4·5 ν. Since the output voltage of the control output terminal 3 is greater than the threshold voltage of q2, Q2 is turned on, and a path is formed between the drain D and the source S of Q2. Since the source S of Q2 is grounded, both the drain D and the source S of Q2 become low level, so that the voltage between the gate 〇_ and the source S of Q1 is the voltage across R3. The absolute value is greater than the threshold voltage of Q1, Q1 is also turned on, the drain D of Q1 and the source S form a path, and the voltage output end 1 of the adapter terminal 150 can supply power to the notebook electric system. If the power adapter is not matched, since the non-knife circuit 30 obtains a suitable voltage division value, the control wheel output terminal 3 having no wheel voltage greater than the threshold voltage of Q2 is not turned on, and Q2 is not turned on, that is, Q2 is regarded as disconnected. Since Q1 is a P-channel enhancement type MOS field effect transistor with negative voltage conduction, when q2 is disconnected, no current flows through R3, that is, the voltage between the gate 源 and the source S of Q1 is zero, so Q1 is not Turning on, therefore, the adapter end 150 12 200820572, ί out 1 can not supply power to the laptop. Compared with the power adapter of the present invention, the system end 100 of the present invention adds two switching circuits 4 形成 formed by the MOSFETs Q1, Q2 and the resistor R3 as switches, and the adapter terminal adds one by two, The emirate, the temple = the star circuit 3〇 formed in series to control the switch circuit 40 k < and the electric _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
'%錢管具有輸人阻抗高、雜訊低、轉定性好、 抗輕射能相、雜小、料工_科便於、好 =該兩個作為開關之電子元件一均採用二 々文應管。 'SCO It) 庫用Μ 為本發明之另—實施例，當該控制電與 二用於糸統端觸所需電壓更高之情況時，開關電路40; 由兩個作為開關之MOS場效應管01、02和兩個電阻R3 R4、、且成’電阻R4串聯在R3 (以之栅極g)和 =本，，電阻一均為高電阻且： 、郎省電此並控制Q1之栅極G、源極S間之電壓大小， Q2在控制輸出端3之作用下導通後，電阻R3、R4組成另 一串聯分壓電路，Q1之栅極G與源極s間之電壓為電陋 R3兩端之電壓，以避免Q1之栅極G與源極s間之 過大而擊穿損壞。 、 如圖4所示，為本發明之又-實施例，該開關電路働 僅由作為卩之P溝道增細MQS場效應管Q1組成，以 之栅極G直接與控制輸出端3相連，調節分壓電路3〇中電 13 200820572 阻R1、R2之大小，使得Q1之柵極G與源極s 之_值（即R1兩端分配之賴）科於Q1之閱值電壓 之絕對值。本實施例中，仍假定系統5〇所需電壓為18v， Qi之閥值電壓為-4V，則可選擇電阻R1之大小為25κ，電 阻R2之大小為75Κ，從*電壓輸出端1與控制輪出端3 之輸出電壓差為4.5V，大於Q1之閥值電壓之絕對值4V， Q1開啟’適配器端100之電壓輸出端i與系統端1〇〇連通 形成供電通路向連接在開關電路40上之系統50供電。 紅上所述，本發明符合發明專利要件，爰依法提出專 利申明。惟，以上所述者僅為本發明之較佳實施例，舉凡 熟悉本案技藝之人士，在爰依本發明精神所作之等效修飾 或變化，皆應涵蓋於以下之申請專利範圍内。 【圖式簡單說明】 圖1係本發明識別電源適配器之控制電路之電路功能 方塊示意圖。 圖2係本發明一實施例中識別電源適配器之控制電路 之電路圖。 圖3係本發明另一實施例中識別電源適配器之控制電 路之電路圖。 圖4係本發明又一實施例中識別電源適配器之控制電 路之電路圖。 圖5係習知技術中電源適配器之電路功能方塊圖。 【主要元件符號說明】 14 200820572 <本發明> 正極輸出端 1+ 降壓電路 10 系統端 100 適配器端 150 負極輸出端 2- 整流電路 20 控制輸出端 3+ 分壓電路 30 開關電路 40,40a，40b 糸統 50 <習知技術> 正極輸出端 1+ 降壓電路 10 負極輸出端 2- 整流電路 20 15'% money tube has high input impedance, low noise, good stability, anti-light energy phase, small, material workers _ department is convenient, good = the two electronic components as switches are used tube. 'SCO It' library Μ is another embodiment of the invention, when the control power and the second voltage required for the system touch are higher, the switch circuit 40; two MOS field effects as switches Tube 01, 02 and two resistors R3 R4, and 'resistor R4 is connected in series at R3 (to gate g) and = this, the resistor one is high resistance and: lang power saves this and controls the gate of Q1 The voltage between the pole G and the source S, Q2 is turned on under the action of the control output 3, the resistors R3 and R4 form another series voltage dividing circuit, and the voltage between the gate G and the source s of Q1 is electric电压 R3 voltage across the R3 to avoid excessive breakdown between the gate G and the source s of Q1. As shown in FIG. 4, in another embodiment of the present invention, the switch circuit 组成 is composed only of a P-channel-thinning MQS field effect transistor Q1 as a 卩, and the gate G is directly connected to the control output terminal 3. Adjusting the voltage divider circuit 3〇中电13 200820572 Resisting the size of R1 and R2, so that the value of the gate G and the source s of Q1 (ie, the distribution of the two ends of R1) is the absolute value of the reference voltage of Q1. . In this embodiment, it is still assumed that the required voltage of the system 5〇 is 18v, and the threshold voltage of Qi is -4V, the size of the resistor R1 can be selected as 25κ, and the size of the resistor R2 is 75Κ, from the *voltage output terminal 1 and control The output voltage difference of the wheel terminal 3 is 4.5V, which is greater than the absolute value of the threshold voltage of Q1 by 4V. Q1 is turned on. The voltage output terminal i of the adapter terminal 100 communicates with the system terminal 1 to form a power supply path to be connected to the switch circuit 40. The system 50 is powered. According to the above description, the invention complies with the requirements of the invention patent, and the patent declaration is filed according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the circuit function of the control circuit for identifying a power adapter of the present invention. Fig. 2 is a circuit diagram showing a control circuit for identifying a power adapter in an embodiment of the present invention. Fig. 3 is a circuit diagram showing a control circuit for identifying a power adapter in another embodiment of the present invention. Fig. 4 is a circuit diagram showing a control circuit for identifying a power adapter in still another embodiment of the present invention. Figure 5 is a block diagram showing the circuit function of the power adapter in the prior art. [Main component symbol description] 14 200820572 <The present invention> Positive output terminal 1+ Buck circuit 10 System terminal 100 Adapter terminal 150 Negative output terminal 2 - Rectifier circuit 20 Control output terminal 3+ Voltage dividing circuit 30 Switching circuit 40 , 40a, 40b 糸 system 50 < conventional technology > positive output terminal 1 + step-down circuit 10 negative output terminal 2 - rectifier circuit 20 15