五、新型說明： 【新型所屬之技術領域】 [0001] 本創作是有關於一種輸入過電壓保護電路，且特別 是一種用於電源供應器的輸入過電壓保護電路。 【先前技術】 [0002] 圖1為一種現有的電源供應器的電路示意圖。請參見 圖1，電源供應器1包括電磁干擾濾波器11 '橋式整流器 1 2、輸入濾波電容器1 3、直流至直流轉換器丨4和輸出濾 波電容器15。交流電源Vac輸入後，通過電磁干擾濾波器 11遽除雜訊’再通過橋式整流器1 2的整流及輸入滅波電 容器13的濾波而轉換成直流輪入電壓V i η。不具調整性的 直流輸入電壓V i η通過直流至直流轉換器14的轉換及輸出 濾波電容器15的濾波而轉換成具調整性的直流輸出電壓 Vout ° 當電源供應器1設計用於接收較低電壓（如ll〇Vrms) 的交流電源Vac時，採用的輪入濾波電容器13的耐壓較低 ，若使用時不小心將其交流插頭插入用於提供較高電壓（ 如220Vrms)的交流電源Vac的插座，則輸入濾波電容器 13將因耐壓不夠而爆炸起火《當然，電源供應器1可採用 耐壓較高的輸入濾波電容器13來防止因耐壓不夠而爆炸 起火，但是其成本當然較高。 【新型内容】 [0003] 本創作的目的就是在提供一種輸入過電壓保護電路 ，可根據電源供應器接收的交流電源電壓的不同自動提 供不同耐壓的輸入濾波電容器。V. New Description: [New Technology Field] [0001] This creation is about an input overvoltage protection circuit, and in particular an input overvoltage protection circuit for a power supply. [Prior Art] [0002] FIG. 1 is a circuit diagram of a conventional power supply. Referring to Fig. 1, the power supply 1 includes an electromagnetic interference filter 11 'bridge rectifier 1 2, an input filter capacitor 13 , a DC to DC converter 丨 4 , and an output filter capacitor 15 . After the AC power supply Vac is input, the noise is removed by the electromagnetic interference filter 11 and converted into the DC input voltage V i η by the rectification of the bridge rectifier 12 and the filtering of the input annihilation capacitor 13. The unregulated DC input voltage V i η is converted to a regulated DC output voltage Vout by the conversion of the DC-to-DC converter 14 and the filtering of the output filter capacitor 15. When the power supply 1 is designed to receive a lower voltage When the AC power supply Vac of (such as ll〇Vrms), the wheel-in filter capacitor 13 used has a low withstand voltage. If it is used, the AC plug is accidentally inserted into the AC power supply Vac for supplying a higher voltage (such as 220Vrms). In the socket, the input filter capacitor 13 will explode due to insufficient withstand voltage. Of course, the power supply 1 can use an input filter capacitor 13 with a high withstand voltage to prevent explosion due to insufficient withstand voltage, but the cost is of course higher. [New Content] [0003] The purpose of this creation is to provide an input over-voltage protection circuit that automatically supplies different withstand voltage input filter capacitors depending on the AC supply voltage received by the power supply.
表單編號A0101 第3頁/共19 I 本創作提出一種輸入過電壓保護電路，其具有第一 端和第二端且並聯耦接以接收直流輸入電壓。輸入過電 壓保護電路包括電壓檢測器、第一電容器、第一開關、 第一電谷器和第二開關，其中電壓檢測器具有第—端、 第一端和輸出端，第一電容器和第二電容器均具有第一 蠕和第二端，第一開關和第二開關均具有第一端、第二 端和控制端。電壓檢測器的第一端和第二端分別耦接輸 入過電壓保護電路的第一端和第二端，電壓檢測器的輸 出端在直流輸入電壓超過閾值時輸出切換信號β第一電 各器的第一端轉接輸入過電壓保護電路的第一端。第一 開關的第一端、第二端和控^|伊別_篆一電容器的 第二端、輸入過電壓保護電檢測器的 輸出端’在接收到切換信號薄第開關采霉通。第二電 容器的第一端耦接第一電容器的第二端。第二開關的第 一端、第二端和控制端分別耦接第二電容器的第二端、 輸入過電壓保護電路的第二端和電壓檢測器的輸出端， 在接收到切換信號時第二開關導通。 本創作因採用根據電源供應器接收的交流電源整流 後的直流輸入電壓的不同，自動切換成第一電容器（其耐 壓較低）或串聯耦接的第一和第二電容器（其耐壓較高）以 提供作為不同耐壓的輸入濾波電容器，可防止因耐壓不 夠而爆炸起火’以較低的成本達到輸入過電壓保護的功 效0 為讓本創作之上述和其他目的、特徵和優點能更明 顯易僅，下文特舉較佳實施例，並配合所附圖式，作詳 細說明如下。 表單編號Α0101 第4頁/共19 1 [0004] 【實施方式】 圖2為採用本創作輸入過電壓保護電路的電源供應器 的電路示意圖。請參見圖2，電源供應器2包括電磁干擾 濾波器21、橋式整流器22、輸入過電壓保護電路23、直 流至直流轉換器24和輸出濾波電容器25。交流電源乂3<2輸 入後’通過電磁干擾濾波器21濾除雜訊，再通過橋式整 流器22的整流及輸入過電壓保護電路23的濾波而轉換成 直流輸入電壓Vin。不具調整性的直流輸入電壓vin通過 直流至直流轉換器24的轉換及輸出濾波電容器25的濾波 而轉換成具調整性的直流輸出電壓Vout。輸入過電壓保 護電路23可根據電源供應器2接收的交流電源Vac電壓的 不同自動提供不同耐壓的輸入濾波電容器，以較低成本 達到輸入過電壓保護功效》 [0005] 圖3為本創作輸入過電壓保護電路的電路示意圖。請 參見圖3，輸入過電壓保護電路23具有第一端231和第二 端232且並聯耦接至如圖2所示橋式整流器22的輸出端以 接收直流輸入電壓Vin。輸入過電壓保護電路23包括電壓 檢測器DET、第一電容器C1、第一開關51、第二電容器 C2和第二開關S2，其中電壓檢測器DET具有第一端IN1、 第一端IN2和輸出端OUT，第一電容器ci和第二電容器C2 均具有第一端和第二端，第一開關Si和第二開關S2均具 有第一端、第二端和控制端》 電壓檢測器DET的第一端INI和第二端^2分別耦接 輸入過電壓保護電路23的第一端231和第二端232，電壓 檢測器DET的輸出端OUT在直流輸入電壓Vin超過閾值時 表單編號A0101 第5頁/共19頁 [0006] 輪出切換信號；反之’在直流輸入電壓V i η未超過閾值時 當然不輪出切換信號。第一電容器C1的第一端耦接輸入 過電壓保護電路23的第一端231。第一開關S1的第一端、 第二端和控制端分別耦接第一電容器C1的第二端、輸入 過電壓保護電路23的第二端232和電壓檢測器DET的輸出 端0UT ’在接收到切換信號時第一開關S1不導通；反之， 在未接收到切換信號時第一開關S1當然導通。第二電容 器C2的第一端耦接第一電容器(^的第二端。第二開關S2 的第一端、第二端和控制端分別耦接第二電容器C2的第 二端、輸入過電壓保護電路23的第二端232和電壓檢測器 DET的輸出端OUT ’在接收到切換信號時第二開關S2導通 .2 V V .' ;反之’在未接收到切換信魏時.第二開關s 2當然不導通 〇 [0007] 在交流電源V a C電壓較高而使直流輸入電壓v i η超過 閾值時，電壓檢測器DET的輸出端OUT輸出切換信號，使 第一開關S1不導通且第二開關S2導通，此時第一電容器 C1和第二電容器C2串聯耦接於輸入過電壓保護電路23的 第一端231和第二端232之間而作為輸入濾波電容器，其 耐壓較高。在交流電源Vac電壓較低而使直流輸入電壓 Vin未超過閾值時，電壓檢測器DET的輸出端OUT不輸出 切換信號’使第一開關S1導通且第二開關S2不導通，此 時僅第一電容器C1耦接於輸入過電壓保護電路23的第一 端231和第二端232之間而作為輸入濾波電容器，其耐壓 較低。 [0008] 圖4為本創作輸入過電壓保護電路的一較佳實施例的 表單編號A0101 第6頁/共19頁 M398288 電路圖。請參見圖4，輸入過電壓保護電路43具有第一端 431和第二端432且並聯耦接以接收直流輸入電壓Vin。 輸入過電壓保護電路43包括電壓檢測器DET、第一電容器 C1、第一開關S1、第二電容器C2和第二開關S2，其中電 壓檢測器DET具有第一端IN1、第二端IN2和輸出端ουτ , 第一電容器Cl和第二電容器C2均具有第一端和第二端， 第一開關S1和第二開關S2均具有第一端 '第二端和控制 端。 輸入過電壓保護電路43還包括第一均壓電阻器只61和 第二均壓電阻器Re2，其中第一均壓電阻器Rel和第二均 壓電阻器Re2均具有第一端和第二端。第一均壓電阻器 Rel的第一端和第二端分別耦接第一電容器C1的第一端和 第二端。第二均壓電阻器Re2的第一端和第二端分別耦接 第二電容器C2的第-端和第二端。第—均虔電阻器㈣和 第一均壓電阻器Re2用於使落在第一電容器。和第二電容 器C2上的電壓均等，防止電壓不均等造成落在某一電容 器上的電愿過高而被擊穿，進而使另_電容器很快亦被 擊穿。 _] 在本實施例中，第-開關S1包括N通道場效應電晶體 Q1，此N通道場效應電晶體具有汲極端、源極端和問極 端且分別耦接第一開關S1的第一端、第二端和控制端。 第二開關S2包括P通道場效應電晶體Q2，此p通道場效應 電晶體Q2具有源極端、祕端和閘極端且分職接第二 開關S2的第、第二端和控制端。此時，輸入過電壓 保濩電路43還包括第一偏壓電阻器Rbl和第二偏壓電阻器 表單編號A0101 第7頁/共丨9頁 I»M3^8288Form No. A0101 Page 3 of 19 I This creation proposes an input overvoltage protection circuit having a first end and a second end coupled in parallel to receive a DC input voltage. The input overvoltage protection circuit includes a voltage detector, a first capacitor, a first switch, a first electric barn, and a second switch, wherein the voltage detector has a first end, a first end, and an output end, the first capacitor and the second The capacitors each have a first creep and a second end, the first switch and the second switch each having a first end, a second end, and a control end. The first end and the second end of the voltage detector are respectively coupled to the first end and the second end of the input overvoltage protection circuit, and the output end of the voltage detector outputs a switching signal β when the DC input voltage exceeds a threshold. The first end of the input is connected to the first end of the overvoltage protection circuit. The first end of the first switch, the second end, and the second end of the control capacitor, the output terminal of the input overvoltage protection electrical detector, receive the switching signal thin switch. The first end of the second capacitor is coupled to the second end of the first capacitor. The first end, the second end, and the control end of the second switch are respectively coupled to the second end of the second capacitor, the second end of the input overvoltage protection circuit, and the output of the voltage detector, and the second end when receiving the switching signal The switch is turned on. The present invention automatically switches to a first capacitor (which has a low withstand voltage) or a series-coupled first and second capacitors (which are more resistant to voltage) by using a DC input voltage that is rectified according to an AC power source received by the power supply. High) to provide input filter capacitors with different withstand voltages, to prevent explosion fire due to insufficient withstand voltage 'to achieve the effect of input overvoltage protection at a lower cost. 0 To make the above and other purposes, features and advantages of the present creation It will be more apparent that the preferred embodiments are described below in detail with reference to the accompanying drawings, which are described in detail below. Form No. Α0101 Page 4/Total 19 1 [Embodiment] FIG. 2 is a circuit diagram of a power supply using the input voltage protection circuit of the present invention. Referring to Fig. 2, the power supply 2 includes an electromagnetic interference filter 21, a bridge rectifier 22, an input overvoltage protection circuit 23, a DC to DC converter 24, and an output filter capacitor 25. After the AC power supply &3<2 is input, the noise is filtered by the electromagnetic interference filter 21, and then converted into a DC input voltage Vin by the rectification of the bridge rectifier 22 and the filtering of the input overvoltage protection circuit 23. The unregulated DC input voltage vin is converted to a regulated DC output voltage Vout by the conversion of the DC to DC converter 24 and the filtering of the output filter capacitor 25. The input overvoltage protection circuit 23 can automatically provide different withstand voltage input filter capacitors according to different AC power supply voltages received by the power supply 2, and achieve input overvoltage protection at a lower cost. [0005] FIG. 3 is a creative input. Schematic diagram of the overvoltage protection circuit. Referring to Figure 3, the input overvoltage protection circuit 23 has a first terminal 231 and a second terminal 232 and is coupled in parallel to the output of the bridge rectifier 22 as shown in Figure 2 to receive the DC input voltage Vin. The input overvoltage protection circuit 23 includes a voltage detector DET, a first capacitor C1, a first switch 51, a second capacitor C2, and a second switch S2, wherein the voltage detector DET has a first terminal IN1, a first terminal IN2, and an output terminal OUT, the first capacitor ci and the second capacitor C2 each have a first end and a second end, and the first switch Si and the second switch S2 each have a first end, a second end, and a first end of the control terminal 》 voltage detector DET The terminal INI and the second terminal ^2 are respectively coupled to the first end 231 and the second end 232 of the input overvoltage protection circuit 23. The output terminal OUT of the voltage detector DET is when the DC input voltage Vin exceeds the threshold. Form No. A0101 Page 5 / Total 19 pages [0006] The switching signal is rotated; otherwise, the switching signal is of course not turned when the DC input voltage V i η does not exceed the threshold. The first end of the first capacitor C1 is coupled to the first end 231 of the input overvoltage protection circuit 23. The first end, the second end and the control end of the first switch S1 are respectively coupled to the second end of the first capacitor C1, the second end 232 of the input overvoltage protection circuit 23, and the output terminal OUT of the voltage detector DET are received The first switch S1 is not turned on when the switching signal is turned on; otherwise, the first switch S1 is of course turned on when the switching signal is not received. The first end of the second capacitor C2 is coupled to the second end of the first capacitor (the second end of the second switch S2, the second end and the control end are respectively coupled to the second end of the second capacitor C2, the input overvoltage The second terminal 232 of the protection circuit 23 and the output terminal OUT of the voltage detector DET are turned on when the switching signal is received. The second switch S2 is turned on. 2 VV .'; otherwise, 'when the switching signal is not received. The second switch s 2 of course, no conduction [0007] When the AC power supply V a C voltage is high and the DC input voltage vi η exceeds the threshold value, the output terminal OUT of the voltage detector DET outputs a switching signal, so that the first switch S1 is non-conducting and second The switch S2 is turned on. At this time, the first capacitor C1 and the second capacitor C2 are coupled in series between the first end 231 and the second end 232 of the input overvoltage protection circuit 23 as an input filter capacitor, and the withstand voltage is high. When the AC power supply voltage is low and the DC input voltage Vin does not exceed the threshold, the output terminal OUT of the voltage detector DET does not output the switching signal 'The first switch S1 is turned on and the second switch S2 is not turned on. At this time, only the first capacitor C1 is coupled to the input overvoltage protection Between the first end 231 and the second end 232 of the circuit 23 as an input filter capacitor, the withstand voltage is low. [0008] FIG. 4 is a form number A0101 of a preferred embodiment of the input overvoltage protection circuit. 6 pages/19 pages M398288 circuit diagram. Referring to Fig. 4, the input overvoltage protection circuit 43 has a first end 431 and a second end 432 and is coupled in parallel to receive a DC input voltage Vin. The input overvoltage protection circuit 43 includes voltage detection. The device DET, the first capacitor C1, the first switch S1, the second capacitor C2 and the second switch S2, wherein the voltage detector DET has a first terminal IN1, a second terminal IN2 and an output terminal ουτ, a first capacitor C1 and a second The capacitor C2 has a first end and a second end, and the first switch S1 and the second switch S2 each have a first end 'the second end and the control end. The input overvoltage protection circuit 43 further includes a first grading resistor only 61 And a second grading resistor Re2, wherein the first grading resistor Rel and the second grading resistor Re2 each have a first end and a second end. The first end and the second end of the first grading resistor Rel Coupling the first end of the first capacitor C1 and the first The first end and the second end of the second voltage equalizing resistor Re2 are respectively coupled to the first end and the second end of the second capacitor C2. The first uniform resistor (4) and the first equalizing resistor Re2 are used for The voltage falling on the first capacitor and the second capacitor C2 is equalized, and the voltage unevenness is prevented from causing the electric power falling on a certain capacitor to be excessively broken, so that the other capacitor is quickly broken down. In the present embodiment, the first switch S1 includes an N-channel field effect transistor Q1 having a 汲 extreme, a source terminal, and an extreme terminal, respectively coupled to the first end of the first switch S1, The second end and the control end. The second switch S2 includes a P-channel field effect transistor Q2 having a source terminal, a secret terminal, and a gate terminal and is coupled to the second, second, and control terminals of the second switch S2. At this time, the input overvoltage protection circuit 43 further includes a first bias resistor Rb1 and a second bias resistor. Form No. A0101 Page 7 of 9 I»M3^8288
Rb2 ’其中第一偏壓電阻器Rbl和第二偏壓電阻器Rb2均 具有第一端和第二端。第一偏壓電阻器Rbl的第一端和第 一端分別耦接輸入過電歷保護電路43的第一端431和電壓 檢測器DET的輸出端OUT。第二偏壓電阻器1^2的第一端 和第一端分別柄接第一偏壓電阻器Rbl的第二端和輸入過 電壓保護電路43的第二端432。第一偏壓電阻器Rbl和第 二偏壓電阻器Rb2用於在電壓檢測器DET的輸出端OUT不 輸出切換信號時，提供偏壓使N通道場效應電晶體Q丨導通 且P通道场效應電晶體Q2不導通〇 [0011] 在本實施例中，電壓檢測器DET包括第一檢測電阻器 Rsl、第二檢測電阻SRs2、第三電容 器C3、電阻器R1和第三開測電阻器 Rsl '第二檢測電阻sRs2、第三電容器㈡和電阻器^均 具有第一端和第二端，齊納二極體Dzl具有陰極端和陽極 知，第二開關S 3具有第一端、第二端和控制端。第一檢 測電阻器Rsl的第一端耦接電壓檢測器DET的第一端IN1 。第二檢測電阻器Rs2的第一端和第二端分別耦接第一檢 測電阻器Rsl的第二端和電壓檢測器DET的第二端IN2。 齊納二極體Dzl的陰極端耦接第二檢測電阻器Rs2的第— 端。第三電容器C3的第一端和第二端分別耦接齊納二極 體Dzl的陽極端和電壓檢測器DET的第二端IN2。電阻器 R1的第一端和第二端分別耦接齊納二極體Dzl的陽極端和 電壓檢測器DET的第二端IN2。第三開關S3的第一端 '第 二端和控制端分別耦接電壓檢測器DET的輸出端〇υτ、電 壓檢測器DET的第二端ΙΝ2和齊納二極體Dzi的陽極端， 表單編號A0101 第8頁/共19頁 在直流輸入電廢Vin超過閾值時第三開關S3導通；反之， 在直流輸入電麈Vin未超過閣值時第三開關^當然不導通 。另外，第三開關S 3包括N通道場效應電晶體Q 3 ’此N通 道場效應電晶體Q3具有沒極端、源極端和問極端且分別 耦接第三開關S3的第一端、第二端和控制端。 [0012] 其中，第〆檢測電阻器Rsl和第二檢測電阻器RS2用 於對直流輸入電廢Vin進行分麼取樣。第三電容器C3用於 在齊納二極體Dzl崩潰導通時對直流輸入電壓Vi η通過第 一檢測電阻器Rs 1和第二檢測電阻器Rs2分壓後的電壓進 行滅波和穩Μ。電阻器R1用於在齊納二極體Dz 1未崩潰時 對第三電容兮〇3進行放電且.提供N通丰·％效應電晶體Q3的 閘極端一路徑斜接輸入過電壓保護電路4 3.的第二端4 3 2而 接地。 [0013] 本創作設計在直流輸入電壓Vin超過閾值時，直流輸 入電壓Vin通過第/檢測電阻器Rsl和第二檢測電阻器 Rs2分壓後的電麈 <使齊納二極想Dzl崩潰導通且N通道場 效應電晶體q3導通，電壓檢測器DET的輸出端OUT通過導 通的N通道場效應電晶體Q3搞接輸入過電壓保護電路43的 第二端432而接地，此時電壓檢測器DET的輸出端OUT因 接地而輸出切換信號（即低準位信號），可使N通道場效應 電晶體Q1不導通且p通道場效應電晶體Q2導通》在直流輸 入電壓Vin未超過閾值時，直流輸入電壓Vin通過第一檢 測電阻器Rs 1和第二檢測電阻器Rs2分壓後的電壓無法使 齊納二極趙Dzl崩濱·導通，故N通道場效應電晶體Q3不導 通，此時電壓檢測器j)ET的輸出端〇υτ相當於開路，通過 表單编號A0101 第9頁/共19頁 [0014]«98288 第一偏壓電阻器Rbl和第二偏壓電阻器Rb2提供偏壓使N通 道場效應電晶體Q1導通且P通道場效應電晶體Q2不導通。 綜上所述，本創作輸入過電壓保護電路通過電壓檢 測器檢測電源供應器接收的交流電源整流後的直流輸入 電壓，在交流電源電壓較高而使直流輸入電壓超過閾值 時，電壓檢測器輸出切換信號，使第一開關不導通且第 二開關導通，以提供串聯耦接的第一電容器和第二電容 器作為輸入濾波電容器，其耐壓較高，在交流電源電壓 較低而使直流輸入電壓未超過閾值時，電壓檢測器不輸 出切換信號，使第一開關導通且第二開關不導通，以提 供第一電容器作為輸入濾波s裔容〜器，其較低。因此 ，本創作輸入過電壓保護電路_據」電操供應谦接收的交 流電源電壓的不同自動提供不同耐壓的輸入濾波電容器 ，可防止因耐壓不夠而爆炸起火，以較低的成本達到輸 入過電壓保護的功效。 [0015] 雖然本創作已以較佳實施例揭露如上，然其並非用 以限定本創作，任何熟習此技藝者，在不脫離本創作之 精神和範圍内，當可作些許之更動與潤飾，因此本創作 之保護範圍當視後附之申請專利範圍所界定者為準。 【圖式簡單說明】 [0016] [0017] [0018] 圖1為一種現有的電源供應器的電路示意圖。 圖2為採用本創作輸入過電壓保護電路.的電源供應器 的電路示意圖。 圖3為本創作輸入過電壓保護電路的電路示意圖。 表單編號A0101 第10頁/共19頁 1398288 [0019] 圖4為本創作輸入過電壓保護電路的一較佳實施例的 電路圖。 【主要元件符號說明】 [0020] 1、2:電源供應器 [0021] 11、21 :電磁干擾濾波器 [0022] 12、22 :橋式整流器 [0023] 13:輸入濾波電容器Rb2' wherein the first bias resistor Rb1 and the second bias resistor Rb2 each have a first end and a second end. The first end and the first end of the first bias resistor Rb1 are respectively coupled to the first end 431 of the input overvoltage protection circuit 43 and the output OUT of the voltage detector DET. The first end and the first end of the second bias resistor 1^2 are respectively connected to the second end of the first bias resistor Rb1 and the second end 432 of the input overvoltage protection circuit 43. The first bias resistor Rb1 and the second bias resistor Rb2 are used to provide a bias voltage to turn on the N-channel field effect transistor Q丨 and the P-channel field effect when the output terminal OUT of the voltage detector DET does not output a switching signal. The transistor Q2 is not conducting 〇 [0011] In the present embodiment, the voltage detector DET includes a first detecting resistor Rs1, a second detecting resistor SRs2, a third capacitor C3, a resistor R1, and a third open measuring resistor Rsl ' The second detecting resistor sRs2, the third capacitor (2) and the resistor have a first end and a second end, the Zener diode Dzl has a cathode end and an anode, and the second switch S3 has a first end and a second end And the control side. The first end of the first detecting resistor Rs1 is coupled to the first end IN1 of the voltage detector DET. The first end and the second end of the second detecting resistor Rs2 are coupled to the second end of the first detecting resistor Rs1 and the second end IN2 of the voltage detector DET, respectively. The cathode end of the Zener diode Dzl is coupled to the first end of the second detecting resistor Rs2. The first end and the second end of the third capacitor C3 are coupled to the anode terminal of the Zener diode Dz1 and the second terminal IN2 of the voltage detector DET, respectively. The first end and the second end of the resistor R1 are coupled to the anode terminal of the Zener diode Dz1 and the second terminal IN2 of the voltage detector DET, respectively. The first end of the third switch S3 and the control end are respectively coupled to the output terminal 〇υτ of the voltage detector DET, the second terminal ΙΝ2 of the voltage detector DET, and the anode terminal of the Zener diode Dzi, the form number A0101 Page 8 of 19 The third switch S3 is turned on when the DC input power waste Vin exceeds the threshold; otherwise, the third switch ^ is of course not turned on when the DC input voltage Vin does not exceed the threshold value. In addition, the third switch S 3 includes an N-channel field effect transistor Q 3 '. The N-channel field effect transistor Q3 has a first end and a second end that are not extreme, source and extreme, and are respectively coupled to the third switch S3. And the control side. [0012] wherein, the second detecting resistor Rs1 and the second detecting resistor RS2 are used for sampling the DC input electric waste Vin. The third capacitor C3 is for canceling and stabilizing the voltage divided by the first sense resistor Rs 1 and the second sense resistor Rs2 when the Zener diode Dzl is turned on. The resistor R1 is used to discharge the third capacitor 兮〇3 when the Zener diode Dz 1 is not collapsed and to provide the gate terminal of the N-passive-% effect transistor Q3, the path slanting input over-voltage protection circuit 4 3. The second end 4 3 2 is grounded. [0013] In the present design, when the DC input voltage Vin exceeds the threshold, the DC input voltage Vin is divided by the first/detection resistor Rs1 and the second detection resistor Rs2, and the Zener diode is considered to be collapsed. The N-channel field effect transistor q3 is turned on, and the output terminal OUT of the voltage detector DET is grounded through the second end 432 of the input overvoltage protection circuit 43 through the turned-on N-channel field effect transistor Q3. At this time, the voltage detector DET The output terminal OUT outputs a switching signal (ie, a low level signal) due to grounding, so that the N-channel field effect transistor Q1 is not turned on and the p-channel field effect transistor Q2 is turned on. When the DC input voltage Vin does not exceed the threshold, the DC The voltage of the input voltage Vin divided by the first detecting resistor Rs 1 and the second detecting resistor Rs2 cannot make the Zener diode Dzl collapse, and the N-channel field effect transistor Q3 is not turned on. The output 〇υτ of the detector j) ET is equivalent to an open circuit, and is biased by the first bias resistor Rbl and the second bias resistor Rb2 via form number A0101 page 9/19 pages [0014]«98288 N-channel field effect transistor Q1 The P-channel field effect transistor Q2 is turned on and turned on. In summary, the input voltage overvoltage protection circuit detects the DC input voltage after the AC power source is rectified by the voltage detector, and the voltage detector outputs when the AC power supply voltage is high and the DC input voltage exceeds the threshold. Switching the signal so that the first switch is non-conducting and the second switch is turned on to provide the first capacitor and the second capacitor coupled in series as an input filter capacitor, which has a high withstand voltage and a DC input voltage at a low AC supply voltage When the threshold is not exceeded, the voltage detector does not output a switching signal, causing the first switch to be turned on and the second switch to be non-conducting to provide the first capacitor as an input filter, which is lower. Therefore, the input voltage protection circuit of the present invention automatically provides different input voltage filter capacitors with different withstand voltages, which can prevent explosions from being fired due to insufficient withstand voltage, and achieve input at a lower cost. The effect of overvoltage protection. [0015] Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this creation is subject to the definition of the scope of the patent application attached. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIG. 1 is a circuit diagram of a conventional power supply. Fig. 2 is a circuit diagram of a power supply using the present input voltage overvoltage protection circuit. FIG. 3 is a schematic circuit diagram of the input overvoltage protection circuit of the present invention. Form No. A0101 Page 10 of 19 1398288 [0019] FIG. 4 is a circuit diagram of a preferred embodiment of the input overvoltage protection circuit. [Main Component Symbol Description] [0020] 1, 2: Power Supply [0021] 11, 21: Electromagnetic Interference Filter [0022] 12, 22: Bridge Rectifier [0023] 13: Input Filter Capacitor
[0024] 14、24 :直流至直流轉換器 [0025] 15、25 :輸出濾波電容器 [0026] 23、43 :輸入過電壓保護電路 [0027] 231、431 :輸入過電壓保護電路的第一端 [0028] 232、432 :輸入過電壓保護電路的第二端 [0029] C1 :第一電容器[0024] 14, 24: DC to DC converter [0025] 15, 25: output filter capacitor [0026] 23, 43: input overvoltage protection circuit [0027] 231, 431: input first end of the overvoltage protection circuit [0028] 232, 432: input second end of the overvoltage protection circuit [0029] C1: first capacitor
[0030] C2 :第二電容器 [0031] C3 :第三電容器 [0032] DET:電壓檢測器 [0033] IN1 :電壓檢測器的第一端 [0034] I N2 :電壓檢測器的第二端 [0035] OUT :電壓檢測器的輸出端 [0036] Dzl :齊納二極體 表單編號A0101 第11頁/共19頁 M398288 [0037] [0038] [0039] [0040] [0041] [0042] [0043] [0044] [0045] [0046] [0047] [0048] [0049] [0050] [0051] Q1、Q 3 . N通道场效應電晶 Q2 : P通道場效應電晶體 R1 :電阻器 Rbl :第一偏壓電阻器 Rb2 :第二偏壓電阻器 Rel :第一均壓電阻器 Re2 :第二均壓電阻器 Rsl :第一檢測電阻器 S »>·：►'；' Rs2 :第二檢測電阻器乂 、義 51 :第一開關 & 52 :第二開關 53 :第三開關 Vac :交流電源 V i η :直流輸入電壓 Vout :直流輸出電壓 體[0030] C2: second capacitor [0031] C3: third capacitor [0032] DET: voltage detector [0033] IN1: first end of the voltage detector [0034] I N2 : second end of the voltage detector [ 0035] OUT : Output of voltage detector [0036] Dzl : Zener diode form number A0101 Page 11 / Total 19 pages M398288 [0037] [0040] [0041] [0042] [0046] [0050] [0010] Q1, Q3. N-channel field effect transistor Q2: P-channel field effect transistor R1: resistor Rbl : first bias resistor Rb2 : second bias resistor Rel : first voltage equalizing resistor Re2 : second voltage equalizing resistor Rsl : first detecting resistor S »>·:►';' Rs2 : Second detecting resistor 乂, meaning 51: first switch & 52: second switch 53: third switch Vac: AC power source V i η : DC input voltage Vout: DC output voltage body
表單編號A0101 第12頁/共19頁Form No. A0101 Page 12 of 19