1364912 六 [0001] [0002] [0003] [0004] [0005] [0006] 100年10月27日按正替換頁發明說明： 【發明所屬之技術領域】 本發明係關於一種開關電源電路。 【先前技術】 開關電源電路具有損耗小、變換效率高、線性變化小、 工作穩定等特點，因此被廣泛應用於液晶電視、陰極射 線管電視等顯示設備及其他消費性電子產品。 明參閱圖1，係一種先前技術開關電源電路之示意圖。該 開關電路1 0包括一第一整流濾波電路1丨、一變壓器1 2、 一第二整流濾波電路1 3及一開關控制電路丨4。 該第一整流濾波電路11包括一全橋整流電路丨丨丨 '一濾波 電容112、二輸入端Π3、114及一輸出端ι15。該二輸入 端113、114用於接收外部交流電壓。該全橋整流電路 111用於將該外部交流電壓轉換為直流電壓。該濾波電容 112 —端接地，另一端連接至該輸出端j 。 該變.墨器12包括一初級繞組丨21及一次級繞組123。該初 級繞組121包括一a端及一b端，其a端連接至該第一整流 濾波電路11之輸出端115，b端經由該開關控制電路η接 地。該次級繞組123包括一c端及一d端。 該第二整流濾波電路13包括一儲能電感131、一儲能電容 132、一第一整流二極體133、一第二整流二極體134及 一直流電壓輪出端135。該儲能電感131之一端連接至該 第一整流二極體133之陰極，另一端連接至該直流電壓輸 出端135。該铸能電容132 —端接地，另一端連接至該直 097119116 表單编號A0101 第5頁/共22頁 1003399145-0 100年.10月·27日修正替無頁 1364912 流電壓輸出端135。該第一整流二極體133之陽極連接至 該次級繞組123之c端，陰極連接至該儲能電感131之一端 。該第二整流二極體134之陽極連接至該次級繞組123之d 端，陰極連接至該儲能電感131之一端。該次級繞組123 之d端接地。 [0007] 該開關控制電路14包括一脈寬調變晶片141、一電晶體 142及一電阻143。該脈寬調變晶片141包括一控制端144 ，該控制端144用於將一脈衝訊號提供給該電晶體142之 閘極。該電晶體142係一N溝道增強型金屬氧化物半導體 場效應電晶體，其閘極連接至該脈寬調變晶片141之控制 端144，源極經由該電阻143接地，汲極連接至該初級繞 組121之b端。 [0008] 該開關電源電路1 0之工作原理如下： [0009] 外部交流電壓輸入至該第一整流濾波電路11之二輸入端 113、114，藉由該第一整流濾波電路11整流、濾波後轉 換為一直流電壓，並提供給該變壓器12之初級繞組121。 該脈寬調變晶片141之控制端144輸出脈衝訊號以控制該 電晶體142之導通或截止，從而控制該變壓器12之工作狀 態。 [0010] 當該電晶體142導通，該濾波電容112、該變壓器之12初 級繞組121、該電晶體142與該電阻143構成一回路，該 第一初級繞組121有導通電流II流過，產生一a端電壓高 於b端電壓之感應電動勢，該次級繞組123產生一c端電壓 高於d端電壓之感應電動勢，從而使該第一整流二極體 097119116 表單编號A0101 第6頁/共22頁 1003399145-0 13.64912 [0011] [0012] [0013] [0014] 097119116 100年.10月27日梭正替換頁 133導通，使該第二整流二極體134截止。該次級繞組 123、該第一整流二極體133、該儲能電感131與該儲能 電容132構成一回路，該儲能電感131有電流12流過。該 儲能電感131及該儲能電容132開始儲能，該次級繞組 123輸出直流電壓。 當該電晶體142由導通變為截止時，該第一初級繞組121 之電流11藉由損耗而逐漸變小，由於電感本身之特性， 該第一初級繞組1 21之電動勢反向，轉變為b端電壓高於a 端電壓，使該第一次級繞組123產生一d端電壓高於c端電 壓之感應電動勢，從而使該第一整流二極體133截止，使 該第二整流二極體134導通。該儲能電感131經由該第二 整流二極體134及該儲能電容132為該直流電壓輸出端 135提供電壓，該儲能電容132為該直流電壓輸出端135 提供電壓。 該開關電源電路1 0係採用該第一整流二極體13 3及該第二 整流二極體134實現整流。惟，該第一整流二極體133及 該第二整流二極體134之導通内阻較大，從而導通損耗較 大，影響該開關電源電路10之效率，不能滿足目前對該 開關電源電路1 0之高效率之需求.。 【發明内容】 有鑑於此，提供一種效率較高之開關電源電路實為必要 〇 一種開關電源電路，其包括一第一整流濾波電路、一第 一變壓器、一開關控制電路及一第二整流濾波電路。該 第二整流濾波電路包括一第一電晶體、一第二電晶體及 表單編號A0101 第7頁/共22頁 1003399145-0 1364912 100年.10月'27日梭正替#頁 一控制電路。其中，外部交流電壓經由該第一整流濾波 電路整流、濾波後轉換為直流電壓並提供給該第一變壓 器，該第一變壓器藉由該開關控制電路之控制輸出直流 電壓至該第二整流濾波電路，該第二整流濾波電路進一 步包括一直流電壓輸出端、一儲能電感及一儲能電容， 該控制電路包括一第一採樣端、一第二採樣端、一第三 採樣端、一第一控制輸出端及一第二控制輸出端，該第 一變壓器包括一第一次級繞組，該第一次級繞組包括一 第一端及一第二端，該第一端依序經由該儲能電感、該 控制電路之第一採樣端及第二採樣端連接至該直流電壓 輸出端，該第一端亦依序經由該第一電晶體之源極、汲 極接地，該第二端依序經由該第二電晶體之汲極、源極 接地，該第三採樣端連接至該直流電壓輸出端，該第一 控制輸出端連接至該第二電晶體之閘極，該第二控制輸 出端連接至該第一電晶體之閘極。該第二整流濾波電路 藉由該控制電路控制該第一電晶體及該第二電晶體之導 通與截止，從而對該第一變壓器輸出之直流電壓進行整 流。 [0015] 一種開關電源電路，其包括一第一變壓器及一整流濾波 電路。該整流濾波電路包括一第一電晶體、一第二電晶 體及一控制電路。該整流濾波電路進一步包括一直流電 壓輸出端、一儲能電感及一儲能電容，該控制電路包括 一第一採樣端、一第二採樣端、一第三採樣端、一第一 控制輸出端及一第二控制輸出端，該第一變壓器包括一 第一次級繞組，該第一次級繞組包括一第一端及一第二 097119116 表單编號Α0101 第8頁/共22頁 1003399145-0 1364912 100年.10月27日修正替换頁 端，該第一端依序經由該儲能電感、該控制電路之第一 採樣端及第二採樣端連接至該直流電壓輸出端，該第一 端亦依序經由該第一電晶體之源極、汲極接地，該第二 端依序經由該第二電晶體之汲極、源極接地，該第二採 樣端連接至該直流電壓輸出端，該第一控制輸出端連接 至該第二電晶體之閘極，該第二控制輸出端連接至該第 一電晶體之閘極。該控制電路用於控制該第一電晶體及 該第二電晶體之導通與截止，從而對該第一變壓器提供 給該整流濾波電路之直流電壓進行整流。 [0016] 相較於先前技術，該開關電源電路係採用控制該第一電 晶體及該第二電晶體之導通與關閉實現整流。該第一電 晶體及該第二電晶體之導通内阻較小，因而導通損耗較 小，對該開關電源電路之效率之影響較小，故該開關電 源電路之效率較高。 【實施方式】 [0017] 請參閱圖2，係本發明開關電源電路一較佳實施方式之示 意圖。該開關電源電路20包括一第一整流濾波電路21、 一第一變壓器22、一第二整流濾波電路23及一開關控制 電路24。 [0018] 該第一整流濾波電路21包括一全橋整流電路211、一第一 濾波電容212、二輸入端213、214及一輸出端215。該二 輸入端213、214用於接受外部交流電壓。該全橋整流電 路211用於將該外部交流電壓轉換為直流電壓。該第一濾 波電容212 —端接地，另一端連接至該輸出端215。 [0019] 097119116 該第一變壓器22包括一第一初級繞組221及一第一次級繞 表單编號A0101 第9頁/共22頁 1003399145-0 1364912 100年10月_2>曰 修正_頁丨. 組223。該第一初級繞組221包括一a端及一b端，其a端 連接至該第一整流濾波電路21之輸出端215，b端經由該 開關控制電路24接地。該第一次級繞組223包括一c端及 一 d端。 [0020] 該第二整流濾波電路23包括一儲能電感231、一第一電晶 體232、一第一保護電阻233、一第二電晶體234、一第 二保護電阻235、一控制電路26、一第三保護電阻236、 一第三電晶體237、一儲能電容238、一第四保護電阻 239及一直流電壓輸出端29。該儲能電感231包括一第一 端2311及一第二端2313，該第一端2311連接至該第一次 級繞組223之c端，該第二端2313連接至該控制電路26。 該第一次級繞組223之c端依序經由該儲能電感231、該控 制電路26、該第三電晶體237之集極、射極連接至該直流 電壓輸出端，亦經由該第一電晶體232之源極、汲極接地 。該第一次級繞組223之d端經由該第二電晶體234之汲極 、源極接地。該儲能電容238與該第四保護電阻239並聯 於該直流電壓輸出端29與地之間。 [0021] 該第一電晶體232及該第二電晶體234均係一N溝道增強型 金屬氧化物半導體場效應電晶體。該第三電晶體237係一 NPN型雙極電晶體，其基極經由該第三保護電阻236連接 至該儲能電感231之第二端2313 » [0022] 該控制電路26包括一第二變壓器261、一第一電阻262、 一第二濾波電容263、一第二電阻264、一第四電晶體 265及一第五電晶體266。該第二變壓器261包括一第二 初級繞組267及一第二次級繞組268。該第二初級繞組 097119116 表單編號 A0101 第 10 頁/共 22 頁 1003399145-0 1364912 • · [0023] [0024] .[0025] 097119116 100年.10月27日按正替换頁 267包括一e端及一f端，其e端連接至該儲能電感231之 第二端2313，f端連接至該第三電晶體237之集極。該第 二次級繞組268包括一g端及一h端’其g端連接至該第一 電阻262，h端連接至該第三電晶體237之射極。該第二電 阻264與該第二濾波電容263並聯於該g端與該h端之間。 該第四電晶體265係一PNP型雙極電晶體，其基極經由該 第一電阻262連接至該第二次級繞組268之g端，射極連接 至該第二次級繞組2 6 8之h端’集極經由該第二保護電阻 235連接至該第二電晶體234之閘極。該第五電晶體266 係一NPN型雙極電晶體，其基極經由該第一電阻262連接 至該第二次級繞組268之g端，射極經由該第一保護電阻 233連接至該第一電晶體232之閘極，集極連接至該第二 次級繞組268之h端。 該控制電路26包括一第一採樣端（未標示）、一第二採樣 端（未標示）、一第三採樣端（未標示）、一第一控制輸出 端（未標示）及一第二控制輸出端（未標示）。該第二初級 繞組267之e端係該控制電路26之第一採樣端。該第二初 級繞組2 6 7之f端係该控制電路2 6之第二採樣端。該第二 次級繞組268之h端係該控制電路26之第三採樣端。該第 四電晶體2 6 5之集極係該控制電路2 6之第一控制輸出端。 該第五電晶體266之射極係該控制電路26之第二控制輸出-端。 該開關控制電路24包括一脈寬調變晶片24丨、一第六電晶 體242及一第三電阻243。該脈寬調變晶片241包括一控 制端244，該控制端244用於將一脈衝訊號提供給該第六 表單編號 A01G1 第 11 頁/共 22 I 1003399145-0 1364912 [loo电10月2>日梭正钥^頁 電晶體242之閘極^該第六電晶體242係一N溝道增強型金 屬氧化物半導體場效應電晶體，其閘極連接至該脈寬調 變晶片241之控制端244，源極經由該第三電阻243接地 ’汲極連接至該第一初級繞組221之b端。 [0026] [0027] [0028] 該第二變壓器261之初次級繞組267、268之匝數比可為1 :100。該第一電阻262之阻值可為1000歐姆。該第二電 阻264之阻值可為1〇〇〇歐姆。該第四保護電阻239之阻值 可為10歐姆。該第二濾波電容263之容值可為1納法拉。 該開關電源電路2 0之工作原理如下： 外部交流電壓輸入至該第一整流濾波電路21之二輸入端 213 ' 214，藉由該第一整流濾波電路21整流、濾波後轉 換為一直流電壓，並提供給該第一變壓器22之第一初級 繞組221。該脈寬調變晶片241之控制端244輸出脈衝訊 號以控制該第六電晶體242之導通或截止，從而控制該第 一變壓器22之工作狀態。 [0029] 當該第六電晶體242導通，該第一濾波電容212、該第一 變壓器22之第一初級繞組221、該第六電晶體242與該第 三電阻243構成一回路’該第一初級繞組221有導通電流 II流過，產生一a端電壓高於b端電壓之感應電動勢’該 第一次級繞組223產生端電壓高於d端電壓之感應電動 勢，使該第三電晶體237導通。該第一次級繞组223、該 儲能電感231、該第二·初級繞組267、該第三電晶體237 、該儲能電容238與該第二電晶體234構成一回路，該儲 能電感231有電流12流過，該第二初級繞組267有電流13 °9711911 表單编號A0101 第12真/共22頁 1003399145-0 13.64912 100年.10月27日修正替換 流過。該儲能電感231及該儲能電容238開始儲能，該第 二初級繞組267產生一e端電壓高於f端電壓之電動勢，因 此該第二次級繞組268之h端電壓高於g端電壓之感應電動 勢’該第四電晶體265導通，該第五電晶體266截止，該 第一次級繞組223之c端之電壓依序經由該儲能電感23i、 該第二初級繞組267、該第三電晶體237之集極及射極、 第四電晶體265之射極及集極輸出至該第二電晶體234之 閘極，使該第二電晶體234導通，該第一次級繞組223輸 出直流電壓。 [0030] 當該第六電晶體242由導通變為截止時，流過該第一初級 繞組221之電流II藉由損耗而逐漸變小，由於電感本身之 特性’該第一初級繞組221之電動勢反向，轉變為b端電 壓高於a端電壓，使該第一次級繞組223產生一d端電壓高 於c端電壓之感應電動勢。此時由於該第三電晶體237及 該第二電晶體234仍處於導通狀態，該第一次級繞組223 、該儲能電感231、該第二初級繞組267、該第三電晶體 237、該儲能電容238與該第二電晶體234構成一回路， 流過該儲能電感231之電流12逐漸變小，流過該第二初級 繞組267之電流13逐漸變小。由於電感本身之特性，該第 二初級繞組267之電動勢反向’轉變為f端電壓高於e端電 壓，因此該第二次級繞組268產生一g端電壓高於h端之感 應電動勢，使該第四電晶體265截止，使該第五電晶體 266導通，從而使該第二電晶體234截止。當流過該儲能 電感231之電流12減小至零並開始反向流動時，該第三電 晶體237截止，該儲能電容238之電壓經由該第五電晶體 097119116 表單編號A0101 第13頁/共22頁 1003399145-0 13649121364912 [0001] [0001] [0003] [0004] [0006] [0006] October 27, 100, according to the replacement page invention: [Technical Field] The present invention relates to a switching power supply circuit. [Prior Art] The switching power supply circuit is widely used in display devices such as LCD TVs, cathode ray tube TVs, and other consumer electronic products because of its low loss, high conversion efficiency, small linear variation, and stable operation. Referring to Figure 1, there is shown a schematic diagram of a prior art switching power supply circuit. The switch circuit 10 includes a first rectification filter circuit 1A, a transformer 1 2, a second rectification filter circuit 13 and a switch control circuit T4. The first rectifying and filtering circuit 11 includes a full bridge rectifying circuit 丨丨丨 'a filter capacitor 112, two input terminals 、3, 114 and an output terminal ι15. The two input terminals 113, 114 are for receiving an external AC voltage. The full bridge rectifier circuit 111 is for converting the external AC voltage into a DC voltage. The filter capacitor 112 is grounded to the other end and connected to the output terminal j. The ink injector 12 includes a primary winding 丨 21 and a primary winding 123. The primary winding 121 includes an a terminal and a b terminal, the a terminal of which is connected to the output terminal 115 of the first rectifying and filtering circuit 11, and the b terminal is grounded via the switching control circuit η. The secondary winding 123 includes a c-end and a d-end. The second rectifying and filtering circuit 13 includes a storage inductor 131, a storage capacitor 132, a first rectifying diode 133, a second rectifying diode 134, and a DC voltage output terminal 135. One end of the energy storage inductor 131 is connected to the cathode of the first rectifying diode 133, and the other end is connected to the DC voltage output terminal 135. The cast capacitor 132 is grounded and the other end is connected to the line. 097119116 Form No. A0101 Page 5 of 22 1003399145-0 100. October 27th Correction No page 1364912 Streaming voltage output 135. The anode of the first rectifying diode 133 is connected to the c-end of the secondary winding 123, and the cathode is connected to one end of the storage inductor 131. The anode of the second rectifying diode 134 is connected to the d terminal of the secondary winding 123, and the cathode is connected to one end of the storage inductor 131. The d terminal of the secondary winding 123 is grounded. The switch control circuit 14 includes a pulse width modulation chip 141, a transistor 142, and a resistor 143. The pulse width modulation chip 141 includes a control terminal 144 for supplying a pulse signal to the gate of the transistor 142. The transistor 142 is an N-channel enhancement type MOS field effect transistor, the gate of which is connected to the control terminal 144 of the pulse width modulation chip 141, the source is grounded via the resistor 143, and the drain is connected to the gate The b-end of the primary winding 121. [0008] The operating principle of the switching power supply circuit 10 is as follows: [0009] The external AC voltage is input to the two input terminals 113, 114 of the first rectifying and filtering circuit 11, and is rectified and filtered by the first rectifying and filtering circuit 11. It is converted to a DC voltage and supplied to the primary winding 121 of the transformer 12. The control terminal 144 of the pulse width modulation chip 141 outputs a pulse signal to control the on or off of the transistor 142, thereby controlling the operating state of the transformer 12. [0010] When the transistor 142 is turned on, the filter capacitor 112, the 12 primary winding 121 of the transformer, the transistor 142 and the resistor 143 form a loop, and the first primary winding 121 has a conduction current II flowing through, generating a The a terminal voltage is higher than the induced electromotive force of the b terminal voltage, and the secondary winding 123 generates an induced electromotive force having a c-terminal voltage higher than the d-terminal voltage, thereby making the first rectifying diode 097119116 form number A0101 page 6 / total 22 pages 1003399145-0 13.64912 [0012] [0014] 097119116 100. On October 27, the shuttle replacement page 133 is turned on, turning off the second rectifying diode 134. The secondary winding 123, the first rectifying diode 133, the storage inductor 131 and the storage capacitor 132 form a loop, and the storage inductor 131 has a current 12 flowing therethrough. The energy storage inductor 131 and the storage capacitor 132 start to store energy, and the secondary winding 123 outputs a DC voltage. When the transistor 142 is turned off by conduction, the current 11 of the first primary winding 121 is gradually reduced by the loss. Due to the characteristics of the inductor itself, the electromotive force of the first primary winding 121 is reversed and converted to b. The terminal voltage is higher than the voltage of the terminal a, so that the first secondary winding 123 generates an induced electromotive force with a voltage of the d terminal higher than the voltage of the c terminal, so that the first rectifying diode 133 is turned off, and the second rectifying diode is turned off. 134 is on. The storage inductor 131 supplies a voltage to the DC voltage output terminal 135 via the second rectifier diode 134 and the storage capacitor 132. The storage capacitor 132 supplies a voltage to the DC voltage output terminal 135. The switching power supply circuit 10 is rectified by the first rectifying diode 13 3 and the second rectifying diode 134. However, the conduction internal resistance of the first rectifying diode 133 and the second rectifying diode 134 is large, so that the conduction loss is large, affecting the efficiency of the switching power supply circuit 10, and cannot meet the current switching power supply circuit 1 0 high efficiency demand. SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a switching power supply circuit with high efficiency. A switching power supply circuit includes a first rectifying and filtering circuit, a first transformer, a switching control circuit, and a second rectification. Filter circuit. The second rectifying and filtering circuit comprises a first transistor, a second transistor and a form number A0101. Page 7 of 22 1003399145-0 1364912 100 years. October '27 day shuttle is a page # a control circuit. The external AC voltage is rectified and filtered by the first rectifying and filtering circuit, and converted into a DC voltage and supplied to the first transformer. The first transformer outputs a DC voltage to the second rectifying and filtering circuit by the control of the switching control circuit. The second rectifying and filtering circuit further includes a DC output terminal, a storage inductor and a storage capacitor. The control circuit includes a first sampling end, a second sampling end, a third sampling end, and a first a control output and a second control output, the first transformer includes a first secondary winding, the first secondary winding includes a first end and a second end, the first end sequentially passes the energy storage The first sampling end and the second sampling end of the control circuit are connected to the DC voltage output end, and the first end is also grounded through the source and the drain of the first transistor sequentially, and the second end is sequentially The third sampling end is connected to the DC voltage output terminal via the drain and the source of the second transistor, and the first control output is connected to the gate of the second transistor, the second control The output is connected to the gate of the first transistor. The second rectifying and filtering circuit controls the on and off of the first transistor and the second transistor by the control circuit to rectify the DC voltage outputted by the first transformer. [0015] A switching power supply circuit includes a first transformer and a rectifying and filtering circuit. The rectifying and filtering circuit includes a first transistor, a second transistor, and a control circuit. The rectifying and filtering circuit further includes a DC output terminal, a storage inductor and a storage capacitor. The control circuit includes a first sampling end, a second sampling end, a third sampling end, and a first control output end. And a second control output, the first transformer includes a first secondary winding, the first secondary winding includes a first end and a second 097119116 Form No. 1010101 Page 8 / Total 22 Page 1003399145-0 1364912 100. On October 27th, the replacement page end is modified, and the first end is sequentially connected to the DC voltage output terminal via the energy storage inductor, the first sampling end and the second sampling end of the control circuit, the first end The second terminal is connected to the DC voltage output terminal via the drain and the source of the second transistor, and the second terminal is sequentially connected to the source and the drain of the first transistor. The first control output is coupled to the gate of the second transistor, and the second control output is coupled to the gate of the first transistor. The control circuit is configured to control the on and off of the first transistor and the second transistor to rectify the DC voltage supplied to the rectifier filter circuit by the first transformer. [0016] Compared to the prior art, the switching power supply circuit performs rectification by controlling conduction and deactivation of the first transistor and the second transistor. The conduction resistance of the first transistor and the second transistor is small, so that the conduction loss is small, and the influence on the efficiency of the switching power supply circuit is small, so the efficiency of the switching power supply circuit is high. [Embodiment] [0017] Please refer to FIG. 2, which is a schematic diagram of a preferred embodiment of a switching power supply circuit of the present invention. The switching power supply circuit 20 includes a first rectifying and filtering circuit 21, a first transformer 22, a second rectifying and filtering circuit 23, and a switching control circuit 24. The first rectifying and filtering circuit 21 includes a full bridge rectifying circuit 211, a first filter capacitor 212, two input terminals 213 and 214, and an output terminal 215. The two inputs 213, 214 are for receiving an external AC voltage. The full bridge rectifier circuit 211 is used to convert the external AC voltage to a DC voltage. The first filter capacitor 212 is grounded and the other end is connected to the output terminal 215. [0019] 097119116 The first transformer 22 includes a first primary winding 221 and a first secondary winding form number A0101 page 9 / total 22 pages 1003399145-0 1364912 100 years October _2 & _ correction _ page ] Group 223. The first primary winding 221 includes an a terminal and a b terminal. The a terminal is connected to the output terminal 215 of the first rectifying and filtering circuit 21, and the b terminal is grounded via the switch control circuit 24. The first secondary winding 223 includes a c-end and a d-end. [0020] The second rectifying and filtering circuit 23 includes a storage inductor 231, a first transistor 232, a first protection resistor 233, a second transistor 234, a second protection resistor 235, a control circuit 26, A third protection resistor 236, a third transistor 237, a storage capacitor 238, a fourth protection resistor 239, and a DC output terminal 29. The energy storage inductor 231 includes a first end 2311 and a second end 2313. The first end 2311 is connected to the c-end of the first secondary winding 223, and the second end 2313 is connected to the control circuit 26. The c-terminal end of the first secondary winding 223 is sequentially connected to the DC voltage output terminal via the energy storage inductor 231, the control circuit 26, and the collector and emitter of the third transistor 237, and also via the first power The source and the drain of the crystal 232 are grounded. The d-end of the first secondary winding 223 is grounded via the drain and source of the second transistor 234. The storage capacitor 238 and the fourth protection resistor 239 are connected in parallel between the DC voltage output terminal 29 and the ground. [0021] The first transistor 232 and the second transistor 234 are both an N-channel enhancement type metal oxide semiconductor field effect transistor. The third transistor 237 is an NPN bipolar transistor whose base is connected to the second end 2313 of the storage inductor 231 via the third protection resistor 236. [0022] The control circuit 26 includes a second transformer. 261. A first resistor 262, a second filter capacitor 263, a second resistor 264, a fourth transistor 265, and a fifth transistor 266. The second transformer 261 includes a second primary winding 267 and a second secondary winding 268. The second primary winding 097119116 Form No. A0101 Page 10 of 22 1003399145-0 1364912 • [0023] [0024] [0025] 097119116 100. October 27 Pressing the replacement page 267 includes an e-end and An f-terminal end is connected to the second end 2313 of the storage inductor 231, and the f-terminus is connected to the collector of the third transistor 237. The second secondary winding 268 includes a g terminal and an h terminal ', the g terminal of which is coupled to the first resistor 262, and the h terminal is coupled to the emitter of the third transistor 237. The second resistor 264 and the second filter capacitor 263 are connected in parallel between the g terminal and the h terminal. The fourth transistor 265 is a PNP type bipolar transistor whose base is connected to the g terminal of the second secondary winding 268 via the first resistor 262, and the emitter is connected to the second secondary winding 2 6 8 The h-th collector is connected to the gate of the second transistor 234 via the second protection resistor 235. The fifth transistor 266 is an NPN-type bipolar transistor, and the base thereof is connected to the g-end of the second secondary winding 268 via the first resistor 262, and the emitter is connected to the first via the first protection resistor 233. A gate of a transistor 232 is connected to the h-end of the second secondary winding 268. The control circuit 26 includes a first sampling end (not labeled), a second sampling end (not labeled), a third sampling end (not labeled), a first control output (not labeled), and a second control. Output (not shown). The e-end of the second primary winding 267 is the first sampling end of the control circuit 26. The f-end of the second primary winding 276 is the second sampling end of the control circuit 26. The h-end of the second secondary winding 268 is the third sampling end of the control circuit 26. The collector of the fourth transistor 265 is the first control output of the control circuit 26. The emitter of the fifth transistor 266 is the second control output terminal of the control circuit 26. The switch control circuit 24 includes a pulse width modulation chip 24A, a sixth transistor 242, and a third resistor 243. The pulse width modulation chip 241 includes a control terminal 244 for providing a pulse signal to the sixth form number A01G1. Page 11 / 22 I 1003399145-0 1364912 [loo electricity October 2 > day The gate of the shuttle transistor 242 is an N-channel enhancement type metal oxide semiconductor field effect transistor whose gate is connected to the control terminal 244 of the pulse width modulation chip 241. The source is grounded via the third resistor 243 and the drain is connected to the b-end of the first primary winding 221. [0028] [0028] The second windings 267, 268 of the second transformer 261 may have a turns ratio of 1:100. The resistance of the first resistor 262 can be 1000 ohms. The resistance of the second resistor 264 can be 1 ohm. The fourth protection resistor 239 may have a resistance of 10 ohms. The second filter capacitor 263 can have a capacitance of 1 nanofarad. The operating principle of the switching power supply circuit 20 is as follows: The external AC voltage is input to the input terminal 213 ' 214 of the first rectifying and filtering circuit 21, and is rectified and filtered by the first rectifying and filtering circuit 21 to be converted into a DC voltage. And supplied to the first primary winding 221 of the first transformer 22. The control terminal 244 of the pulse width modulation chip 241 outputs a pulse signal to control the on or off of the sixth transistor 242, thereby controlling the operating state of the first transformer 22. [0029] When the sixth transistor 242 is turned on, the first filter capacitor 212, the first primary winding 221 of the first transformer 22, the sixth transistor 242 and the third resistor 243 form a loop 'the first The primary winding 221 has an on current II flowing through it, generating an induced electromotive force having a voltage at the a terminal higher than the voltage at the b terminal. The first secondary winding 223 generates an induced electromotive force having a terminal voltage higher than the voltage at the d terminal, so that the third transistor 237 Turn on. The first secondary winding 223, the storage inductor 231, the second primary winding 267, the third transistor 237, the storage capacitor 238 and the second transistor 234 form a loop, and the storage inductor 231 has a current 12 flowing through, the second primary winding 267 has a current of 13 ° 9711911 Form No. A0101 No. 12 true / total 22 pages 1003399145-0 13.64912 100 years. October 27 correction replacement flow. The storage inductor 231 and the storage capacitor 238 start to store energy, and the second primary winding 267 generates an electromotive force whose e-terminal voltage is higher than the f-terminal voltage, so that the h-terminal voltage of the second secondary winding 268 is higher than the g-terminal. The induced electromotive force of the voltage 'the fourth transistor 265 is turned on, the fifth transistor 266 is turned off, and the voltage at the c-end of the first secondary winding 223 is sequentially passed through the storage inductor 23i, the second primary winding 267, The collector and the emitter of the third transistor 237, the emitter and the collector of the fourth transistor 265 are output to the gate of the second transistor 234, and the second transistor 234 is turned on. The first secondary winding 223 output DC voltage. [0030] When the sixth transistor 242 is turned off from on, the current II flowing through the first primary winding 221 is gradually reduced by the loss, and the electromotive force of the first primary winding 221 is due to the characteristic of the inductor itself. In the reverse direction, the voltage at the b-side is higher than the voltage at the terminal a, so that the first secondary winding 223 generates an induced electromotive force whose voltage at the d terminal is higher than the voltage at the c-terminal. At this time, since the third transistor 237 and the second transistor 234 are still in an on state, the first secondary winding 223, the energy storage inductor 231, the second primary winding 267, the third transistor 237, the The storage capacitor 238 and the second transistor 234 form a loop, the current 12 flowing through the storage inductor 231 gradually becomes smaller, and the current 13 flowing through the second primary winding 267 gradually becomes smaller. Due to the characteristics of the inductor itself, the electromotive force of the second primary winding 267 is reversed to a voltage at which the f terminal voltage is higher than the voltage at the e terminal, so that the second secondary winding 268 generates a g-terminal voltage higher than the induced electromotive force at the h terminal, so that The fourth transistor 265 is turned off to turn on the fifth transistor 266, thereby turning off the second transistor 234. When the current 12 flowing through the storage inductor 231 decreases to zero and begins to flow in the opposite direction, the third transistor 237 is turned off, and the voltage of the storage capacitor 238 is via the fifth transistor 097119116. Form No. A0101 Page 13 / Total 22 pages 1003399145-0 1364912
1^〇年1〇月_27曰梭正替私頁I 266之集極、射極輸出至該第一電晶體232之閘極’使該 第一電晶體232導通，從而該儲能電感23i經由該第一電 晶體232及該第六電阻239為該直流電壓輸出端29提供電 壓，該儲能電容238為該直流電壓輸出端29提供電壓》 [0031] 相較於先前技術，該開關電源電路20係採用控制該第一 電晶體232及該第二電晶體234之開啟與關閉實現整流。 該第一電晶體232及該第二電晶體234之導通内阻較小， 因而導通損耗較小，對該開關電源電路20之效率之影響 - 較小’故該開關電源電路20之效率較高。 [0032] 本發明之開關電源電路20亦可具其他多種變更設計，如 :較佳實施方式之第三電晶體237及第四電晶體265亦可 為N溝道金屬氧化物半導體場效應電晶體，第五電晶體 266亦可為p溝道金屬氧化物半導體場效應電晶體。較佳 實施方式之脈寬調變晶片241亦可由一可產生脈衝訊號之 脈衝產生電路代替，該脈衝產生電路連接至該第六電晶 體242之閘極。 [0033] 綜上所述，本發明確已符合發明專利之要件，爰依法提 出專利申請。惟，以上所述者僅為本發明之較佳實施方 式，本發明之範圍並不以上述實施方式為限，舉凡熟悉 本案技藝之人士援依本發明之精神所作之等效修飾或變 化，皆應涵蓋於以下申請專利範圍内。 【圖式簡單說明】 [0034] 圖1係一種先前技術開關電源電路之示意圖。 [0035] 圖2係本發明開關電源電路一較佳實施方式之示意圖。 097119116 表單编號A0101 第14頁/共22頁 1003399145-0 13.64912 100年10月2>日梭正替換頁 【主要元件符號說明】 [0036] 開關電源電路：2 0 [0037] 第一整流濾波電路：21 [0038] 全橋整流電路：211 [0039] 第一濾波電容：2 1 2 [0040] 輸入端：213、214 [0041] 輸出端：215 [0042] 第一變壓器：22 [0043] 第一初級繞組：221 [0044] 第一次級繞組：223 [0045] 第二整流濾波電路：23 [0046] 儲能電感：231 [0047] 第一端：2311 [0048] 第一電晶體：232 [0049] 第二端：2313 [0050] 第一保護電阻：233 [0051] 第二電晶體：234 [0052] 第二保護電阻：235 [0053] 第三保護電阻：236 [0054] 第三電晶體：237 097119116 表單編號A0101 第15頁/共22頁 1003399145-0 1364912 [0055] 儲能電容：238 [0056] 第四保護電阻：239 [0057] 直流電壓輸出端：29 [0058] 控制電路：26 [0059] 第二變壓器：261 [0060] 第二初級繞組：267 [0061] 第二次級繞組：268 [0062] 第一電阻：2 6 2 [0063] 第二耦合電容：263 [0064] 第二電阻：264 [0065] 第四電晶體：265 [0066] 第五電晶體：266 [0067] 開關控制電路：24 [0068] 脈衝調變晶片：241 [0069] 控制端：244 [0070] 第六電晶體：242 [0071] 第三電阻：243 097119116 表單編號A0101 第16頁/共22頁 ΙΟΟΐρ ίΟ月，2>曰核正替_頁 1003399145-01^〇年1〇月_27曰 Shuttle is the collector of the private page I 266, and the emitter is output to the gate of the first transistor 232' to turn on the first transistor 232, so that the energy storage inductor 23i The DC voltage output terminal 29 is supplied with a voltage via the first transistor 232 and the sixth resistor 239, and the storage capacitor 238 supplies a voltage to the DC voltage output terminal 29. [0031] Compared to the prior art, the switching power supply The circuit 20 performs rectification by controlling the opening and closing of the first transistor 232 and the second transistor 234. The conduction resistance of the first transistor 232 and the second transistor 234 is small, so that the conduction loss is small, and the influence on the efficiency of the switching power supply circuit 20 is small. Therefore, the efficiency of the switching power supply circuit 20 is high. . [0032] The switching power supply circuit 20 of the present invention may also have various other modifications. For example, the third transistor 237 and the fourth transistor 265 of the preferred embodiment may also be N-channel MOSFETs. The fifth transistor 266 can also be a p-channel metal oxide semiconductor field effect transistor. The pulse width modulation chip 241 of the preferred embodiment may also be replaced by a pulse generating circuit that generates a pulse signal, and the pulse generating circuit is connected to the gate of the sixth transistor 242. [0033] In summary, the present invention has indeed met the requirements of the invention patent, and the patent application is filed according to law. However, the above description is only the preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention are It should be covered by the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS [0034] FIG. 1 is a schematic diagram of a prior art switching power supply circuit. 2 is a schematic diagram of a preferred embodiment of a switching power supply circuit of the present invention. 097119116 Form No. A0101 Page 14/Total 22 Page 1003399145-0 13.64912 October 2, 2> Risotto Replacement Page [Main Component Symbol Description] [0036] Switching Power Supply Circuit: 2 0 [0037] First Rectification Filter Circuit : 21 [0038] Full-bridge rectifier circuit: 211 [0039] First filter capacitor: 2 1 2 [0040] Input: 213, 214 [0041] Output: 215 [0042] First transformer: 22 [0043] A primary winding: 221 [0044] First secondary winding: 223 [0045] Second rectifying and filtering circuit: 23 [0046] Energy storage inductance: 231 [0047] First end: 2311 [0048] First transistor: 232 Second end: 2313 [0050] First protection resistor: 233 [0051] Second transistor: 234 [0052] Second protection resistor: 235 [0053] Third protection resistor: 236 [0054] Third power Crystal: 237 097119116 Form No. A0101 Page 15 of 22 1003399145-0 1364912 [0055] Storage Capacitor: 238 [0056] Fourth Protection Resistor: 239 [0057] DC Voltage Output: 29 [0058] Control Circuit: 26 [0059] Second Transformer: 261 [0060] Second Primary Winding: 267 [0061] Second Secondary Winding: 268 [0062] One resistor: 2 6 2 [0063] Second coupling capacitor: 263 [0064] Second resistor: 264 [0065] Fourth transistor: 265 [0066] Fifth transistor: 266 [0067] Switch control circuit: 24 [ 0068] Pulse Modulation Wafer: 241 [0069] Control Terminal: 244 [0070] Sixth Transistor: 242 [0071] Third Resistor: 243 097119116 Form No. A0101 Page 16 of 22 ΙΟΟΐρ ίΟ月,2>曰Nuclear replacement _ page 1003399145-0