201010497 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種LED驅動電路，特別是關於一種單級 具零電壓切換之LED驅動電路。 【先前技術】 隨著目前LED應用於照明及顯示器背光源的發展趨勢， 已有許多針對LED特性的驅動電路相關專利（參考先前技術 [1-3])。在這些驅動電路架構之中，主要單純針對驅動 LED的效月b ’進行提昇。但在目前產業上，由於整個電器 產品的整體考量，會在驅動電路上，額外要求。習知LED 驅動電路電源取自市電輸入，因安規要求，輸入與輸出端 需電氣隔離，並且有時候因須同時驅動不同的LED (R’G’B)’需二組不同的電壓。因此，為了達到電氣隔離 與個別驅動的要求’習知電路設計成兩級電路來驅動 LED(參考先前技術[4])。 參考圖1 ’其顯示習知LED驅動電路之方塊示意圖。習 知LED驅動電路10包括：一被動濾波器u、一前級功因 修正電路12及一後級多繞組輸出隔離式轉換器13。習知 LED驅動電路10用以驅動多組或多色LED 14，該LED組14 包括紅色LED 141、綠色LED 142及藍色LED 143。交流市 電經被動濾波器11之後’為滿足功因安規要求，利用該前 級功因修正電路12達到高功因之功效，並再利用該後級多 繞組輸出隔離式轉換器13，例如升壓式轉換器、降壓式轉 換器（Buck converter)及降升壓式轉換器（Buck-boost 131001.doc 201010497 converter)，達到多組電壓輸出（參考先前技術[5])。 在先前技術[1 ]中，雖然可以達到高功因的成效，但是 卻無法兼顧電氣隔離的問題。在這些習知LED驅動電路架 構下，由於切換開關無法零電壓切換，因此開關損耗明 顯’使得電路效率降低。 因此，有必要提供一種創新且具進步性的單級具零電壓 切換之LED驅動電路，以解決上述問題。201010497 IX. Description of the Invention: [Technical Field] The present invention relates to an LED driving circuit, and more particularly to a single-stage LED driving circuit with zero voltage switching. [Prior Art] With the current development trend of LEDs for lighting and display backlights, there have been many patents related to driving circuits for LED characteristics (refer to the prior art [1-3]). Among these drive circuit architectures, the main purpose is to improve the efficiency of driving LEDs. However, in the current industry, due to the overall consideration of the entire electrical products, there will be additional requirements on the drive circuit. The conventional LED driver circuit power supply is taken from the mains input. Because of the safety requirements, the input and output terminals need to be electrically isolated, and sometimes two different voltages are required to drive different LEDs (R'G'B). Therefore, in order to achieve the requirements of electrical isolation and individual drive, the conventional circuit is designed as a two-stage circuit to drive the LED (refer to the prior art [4]). Referring to Figure 1 '', a block diagram of a conventional LED driver circuit is shown. The conventional LED driving circuit 10 includes a passive filter u, a pre-stage power factor correcting circuit 12, and a post-stage multi-winding output isolated converter 13. The LED driving circuit 10 is used to drive a plurality of groups or multi-color LEDs 14, and the LED group 14 includes a red LED 141, a green LED 142, and a blue LED 143. After the AC power is passed through the passive filter 11, 'to meet the safety requirements of the power factor, the pre-stage power factor correction circuit 12 is used to achieve high power efficiency, and the post-stage multi-winding output isolation converter 13 is used again, for example, boosting Converter, Buck converter and Buck-boost 131001.doc 201010497 converter, to achieve multiple sets of voltage output (refer to the prior art [5]). In the prior art [1], although the effect of high power can be achieved, the problem of electrical isolation cannot be taken into account. Under these conventional LED driving circuit architectures, since the switching switch cannot be switched to zero voltage, the switching loss is markedly reduced, so that the circuit efficiency is lowered. Therefore, it is necessary to provide an innovative and progressive single-stage LED drive circuit with zero voltage switching to solve the above problems.
先前技術： [1] 中華民國專利公開第200704284號，專利名稱：驅動 LED的單級數位功率轉換器。 [2] 中華民國專利公開第200522794號，專利名稱：發光 二極體驅動電路。 [3] 中華民國專利公開第200703 183號，專利名稱：發光 二極體驅動電路。 [4] S.Muthu and J. Gaines, uRed, Green and Blue LED-Based White Light Source: Implementation Challenges and Control Design”，IEEE Industry ApplicationsPrior Art: [1] Republic of China Patent Publication No. 200604284, Patent Name: Single-stage digital power converter for driving LEDs. [2] Republic of China Patent Publication No. 200522794, Patent Name: Light-emitting diode drive circuit. [3] Republic of China Patent Publication No. 200603 183, Patent Name: Light-emitting diode drive circuit. [4] S. Muthu and J. Gaines, uRed, Green and Blue LED-Based White Light Source: Implementation Challenges and Control Design”, IEEE Industry Applications
Conference, 2003, pp. 515-522.Conference, 2003, pp. 515-522.
[5] 周志敏，周紀海，紀愛華，屦鳶f*路設#/輿薦 房，上海郵電出版社，2006年。 【發明内容】 本發明在於提供一種單級具零電壓切換之LED驅動電 路，包括：一功因修正電路及一具零電壓切換之隔離式轉 換器。該功因修正電路用以接收一交流輸入電壓，以修正 131001.doc 201010497 功因。該具零電壓切換之隔離式轉換器連接該功因修正電 路’其具有至少一切換開關，該切換開關係為零電壓切 換’該隔離式轉換器用以將交流輸入電壓轉換為至少一直 流輸出電壓，以驅動至少一 LED。 本發明之單級具零電壓切換之LED驅動電路將功因修正 電路與隔離式轉換器進行整合，隔離式轉換器内之部分元 件與功因修正電路之部分元件相同。功因修正電路之電感 ❿ 工作於不連續導通模式（Discontinuous conduction mode， DCM)之下’可使功率因數接近丨。且該隔離式轉換器工作 於電感性負載模式之下，使所有的主動開關均具有零電壓 切換（Zero voltage switching, ZVS)導通的優點，降低主動 開關的切換損失。因此，本發明之單級具零電壓切換之 LED驅動電路具高功因、高電路效率及具有減少電路元件 與降低成本之功效。 【實施方式】 Φ 參考圖2’其顯示本發明之單級具零電壓切換之lEd媒 動電路之示意圖。本發明之單級具零電壓切換之led驅動 電路22包括：一功因修正電路221及一具零電壓切換之隔 離式轉換器222。該功因修正電路22丨用以接收一交流輸入 -電壓’以修正功因。該具零電壓切換之隔離式轉換器222 • 連接該功因修正電路，其具有至少一切換開關，該切換開 關係為零電壓切換’該隔離式轉換器用以將交流輸入電壓 轉換為至少一直流輸出電壓，以驅動至少一 [ΕΕ)。在本發 明實施例中，該具零電壓切換之隔離式轉換器222可為一 131001.doc 201010497 具多繞組輸出及零電壓切換之隔離式轉換器，以提供複數 個直流輸出電壓，驅動多組或多色LED 24，該LED組24包 括紅色LED 241、綠色LED 242及藍色LED 243。 本發明之單級具零電壓切換之LED驅動電路22另包括一 被動滤波器21，用以濾除高頻成分，被動濾波器21連接於 該交流輸入電壓及該功因修正電路221之間。 參考圖3’其顯示本發明單級具零電壓切換之led驅動 φ 電路第一實施例之電路示意圖。在本發明第一實施例單級 具零電壓切換之LED驅動電路30中，該功因修正電路係為 升壓式功因修正電路’該隔離式轉換器係為隔離式正半橋 諧振轉換器。該被動濾波器包括一濾波電感Lf及一濾波電 容Cf。 該功因修正電路包括：一第一整流二極體Drl、一第二 整流二極體Dr2、一第一電感、一第一切換開關、一 第二切換開關Q2、一第一電容q及一第二電容c2;其中該 ❹ 第一整流二極體Dri與該第二整流二極體Dr2連接；該第一 切換開關Q!與該第二切換開關A連接，且與該第一整流二 極體Dri及該第一整流·__極體Dr2並聯連接；該第》__電容c ^ 與該第二電容C2連接，且與該第一切換開關仏及該第二切 ，換開關Q2並聯；該第一電感L!連接於該被動濾波器及該第 一切換開關仏與該第二切換開關A之連接點a之間。 該具零電壓切換之隔離式轉換器包括：該第一切換開關 Qi、該第二切換開關Q2、該第一電容Ci、該第二電容C2、 一第三電容Cr、一第三電感Lr、一變壓器τ及一整流器R。 131001.doc •9- 201010497 本發明之單級具零電壓切換之led驅動電路將功因修正電 , 路與隔離式轉換器進行整合，在隔離式轉換器内之部分元 件與功因修正電路之部分元件相同’在本實施例中，該具 零電壓切換之隔離式轉換器之該第一切換開關Q1、該第二 切換開關Q2、該第一電容q及該第二電容c2係與該功因修 正電路之該第一切換開關Qi、該第二切換開關q2、該第一 電容及該第二電容c2相同。 φ 在本實施例中’該第三電容cr及該第三電感Lr連接，並 連接至該第一切換開關Q,與該第二切換開關Q2之連接點 a;該變壓器T連接於該第三電感Lr及該第一電容Ci與該第 二電容C2之連接點b之間；該整流器r連接至該變壓器τ。 該整流器R包括四個整流二極體Dr5、Df6、Da及Du。該變 壓器T可為多繞組輸出變壓器，以提供複數個直流輸出電 壓’驅動複數個LED。 以下說明本發明第一實施例單級具零電壓切換之lEd驅 ❹ 動電路之工作模式： (1)工作模式I : 當驅動訊號Fgi；2將該第二切換開關q2截止時，即進入工 作模式I。在經過短暫的怠遲時間後，該第一切換開關 之驅動訊號匕sl由低電位變為高電位，該第一切換開關Qi • 並未立即導通。因為將諧振迴路設計於電感性，諧振電流 h將落後電壓，所以在該第二切換開關A截止的瞬間，^ 為負值並逆向流經二極體(可利用]^〇81^丁之基底-汲極 間的一極體來作為仏和]^，毋需額外並聯二極體p 一旦 131001.doc 10- 201010497 D!導通’整流後之輸人電壓跨在該第__電感Q ,電感電 流/η從零開始線性增加，L增加的速度與輪人電壓成正 比起初，Zil較小’…與。之合成電流仍為逆向，Di繼 續導通。备！£1上升至使/si轉為正向時，D!戴止該第一切 換開關Q,才導通，進入工作模式„。因為該第—切換開關 QA換導通時電㈣於零，具有零電壓切換導通之優點， 大幅度降低了切換損失。 ^ (2)工作模式II: 在該第一切換開關Ql導通時，該第一電感£ι兩端電壓仍 然等於整流後之輸入電壓，電感電流^持續線性增加，而 譜振電流㈣由負值漸漸振盈至正值。“為正值之後， h與，·，共同流過該第一切換開關Qi。當該第一切換開關Qi 截止時，電感電流h到達這個週期的峰值，接著進入工作 模式ΠΙ。 (3)工作模式ΠΙ : • it入工作模式m時，&為正值，電流路徑由該第一切換 開關Q!轉換到二極體A，並對該第二電容〇充電❶另一方 面，電感電流h流經D2，同時對該第一電容q、該第二電 容〇充電。該第一電感A兩端電壓OMM負值，…從 2值開始線性下降。為了使轉換器工作於DCM，該第-電 谷。丨與該第二電容C2兩端電壓和⑹必須大於交流輸入電 壓”5的峰值兩倍以上。 因為h的峰值與交流輸入電壓〜成正比，所以心下降至 零的時間隨著輸入電壓的變化而不同。若h比心晚下降至 131001.doc -11 - 201010497 零，進入工作模式IV-a;反之，當…比g早下降至零則 進入工作模式IV-b » (4) 工作模式IV-a : 當交流輸入電壓vs在較高電壓時，振盪至零後反向， 此時，電感電流h持續線性下降。當G再振盪到比“大 時，該第二切換開關Q2導通，反向的&與心的差流經該第 二切換開關Q2。在驅動訊號變為低電位之前，電感電 魯 流會先下降到零，接著進入工作模式v。 (5) 工作模式IV-b : 當交流輸入電壓v,於較低電壓時，仏會先降為零，電源 停止輸入電流。此時’ ^仍為正值，並持續流經D2，直到 k振盪經過零點變為負值時，該第二切換開關匕隨仏截止 切換導通，接著進入工作模式V。 (6) 工作模式V : 此時該第二切換開關Q2導通，Ζ·Λ為負且流經該第二切換 ❹ 開關Q2,第二電容Q提供能量給諧振迴路，當~s2由高電 位變為低電位瞬間，該第二切換開關A載止，電路則回到 下一高頻週期的工作模式I。 因此，不論從在工作模式πι進入模式1¥_&，或是從工作 模式III進入模式灰-b，再到模式V。在該第二切換開關Q2 導通之則，h為正值且流經〇2，Q2兩端所跨電壓幾乎為 零，因此，該第二切換開關Q2可達成零電壓切換導通。由 上述工作模式分析可發現，該第一切換開關Q1及該第二切 換開關Q2均具有零電壓切換導通的優點，可以大幅度降低 131001.doc -12- 201010497 切換損失。因此，本發明之單級具零電壓切換之LED驅動 電路具高功因，高電路效率及具有減少電路元件與降低成 本之功效。 參考圖4，其顯示本發明單級具零電壓切換之LED驅動 電路第二實施例之電路示意圖。在本發明第二實施例單級 具零電壓切換之LED驅動電路40中，該功因修正電路係為 升壓式功因修正電路，該隔離式轉換器係為隔離式準半橋 ❹ 諧振轉換器。與第一實施例不同之處在於，第二實施例單 級具零電壓切換之LED驅動電路40不具有第二電容c2。因 此’第二實施例單級具零電壓切換之Led驅動電路40具有 第一實施例單級具零電壓切換之LED驅動電路3〇之功效。 參考圖5，其顯示本發明單級具零電壓切換之lED驅動 電路第三實施例之電路示意圖。在本發明第三實施例單級 具零電壓切換之LED驅動電路50中’該功因修正電路係為 降升壓式功因修正電路’該隔離式轉換器係為隔離式正半 φ 橋諧振轉換器。 該功因修正電路包括：一第一整流二極體Drl、一第二 整流二極體Dr2、一第三整流二極體D3、一第四整流二極 艎D4、一第一電感Lpl、一第二電感Lp2、一第一切換開關 Qi、一第二切換開關Q2、一第一電容及一第二電容C2 ; .其中該第一整流二極體Drl與該第二整流二極體Dr2連接； 該第一切換開關Q,與該第二切換開關q2連接；該第一電容 G與該第二電容C2連接，且與該第一切換開關（^及該第二 切換開關Q2並聯；該第一電感[^連接於該第一整流二極 131001.doc •13· 201010497 體Drl與該第一切換開關Q〗之間；該第二電感Lp2連接於該 第二整流二極體Du與該第二切換開關Q2之間；該第三整 流二極體D3與該第四整流二極體D4連接，且與該第一整流 二極體Drl及該第二整流二極體Dr2並聯連接。。 該具零電壓切換之隔離式轉換器包括：該第一切換開關 Q!、該第二切換開關Q2、該第一電容Cl、該第二電容C2、 一第二電容cr、一第三電感Lr、該第三整流二極體d3、該 φ 第四整流二極體D4、一變壓器T及一整流器R。本發明之 單級具零電壓切換之LED驅動電路將功因修正電路與隔離 式轉換器進行整合，在隔離式轉換器内之部分元件與功因 修正電路之部分元件相同’在本實施例中，該具零電壓切 換之隔離式轉換器之該第一切換開關Q】、該第二切換開關 Q2、該第三整流二極體D3、該第四整流二極體d4、該第一 電容C!及該第二電容c2係與該功因修正電路之該第一切換 開關Q!、該第二切換開關Q2、該第三整流二極體〇3、該第 Q 四整流二極鱧d4、該第一電容q及該第二電容C2相同。 在本實施例中，該第三電容Cr及該第三電感Lr連接，並 連接至該第一切換開關仏與該第二切換開關（)2之連接點 a;該變壓器T連接於該第三電感Lr及該第一電容C,與該第 . 二電容C2之連接點b之間；該整流器R連接至該變壓器T。 該整流器包括四個整流二極鱧Dr5、Dr6、Dr7及Dr8。該變壓 器可為多繞組輸出變壓器，以提供複數個直流輸出電壓， 驅動複數個LED。 以下說明本發明第三實施例單級具零電壓切換之LED驅 131001.doc • 14· 201010497 動電路之工作模式： (1)工作模式I : 當驅動訊號匕2將該第二切換開關Q2截止時，即進入工 作模式I。在經過短暫的怠遲時間後，該第_切換開㈣ 之驅動訊號h由低電位變為高電位，該第_切換開叫 並未立即導通。因為將諧振迴路設計於電感性，谐振電流 b將落後電壓，所以在該第二切換開關Q2截止的瞬間，G ❹ 為負值並逆向流經二極體D〗（可利用MOSFET之基底汲極 間的一極體來作為仏和D2，毋需額外並聯二極體p 一旦 導通，整流後之輸入電壓跨在該第一電感Lpi上，電感 電流從零開始線性增加，增加的速度與輸入電壓成 正比。起初，ζζρ1較小，"…與心之合成電流h仍為逆向， 〇!繼續導通。當h上升至使/si轉為正向時，截止，該第 一切換開關才導通，進入工作模式〗〗。因為該第一切換 開關（^切換導通時電壓等於零，具有零電壓切換導通之優 點，大幅度降低了切換損失。 (2)工作模式II : 進入工作模式II的瞬間，該第一切換開關Qi導通，該第 一電感兩端電壓仍然等於整流後之輸入電壓，電感電 流Upl持續線性増加，而諧振電流&則由負值漸漸振盪至正 值°當ίΛ為正值之後’ Qpl與心共同流過該第一切換開關 Q!。當驅動電壓Fg5l轉為低準位時，該第一切換開關（^截 止’電感電流Qpl到達這個週期的峰值，接著進入工作模 式 III。 13ia01.doc -15- 201010497 (3)工作模式Hi : 《了使轉換器工作於DCM，必須設計該第-電容C!兩端 ， ㈣M(^/2)大於交流輸人電&的峰值，使該第一整流 一極體Drl逆向偏壓。此時，第一電感電流心i將不再流過 輸入電源，而是流經該第三整流二極體〇3，並對該第一電 容〇充電。由於此時第一電感兩端所跨之電壓為負值（_ 匕c/2) ’第一電感電流心〗從峰值開始線性下降。又因為第 φ 一電感電流…1的峰值與輸入電壓v,成正比關係，所以第一 電感電流ζΖρ1下降至零的時間隨著輸入電壓〜的變化而不 同。若第一電感電流比晚下降至零，進入工作模式 IV-a，反之，當第一電感電流比&早下降至零，則進入 工作模式IV-b。進入工作模式〗„時//?為正值，&的電流路 徑由該第一切換開關Ql轉換到二極體d2，並對該第二電容 c2充電。 (4) 工作模式iv-a : φ 工作模式1V-a是發生於輸入電壓在較高電壓時，此時， 該第二切換開關Q2導通，該第二切換開關G流經Q2。而第 電感Zpi兩端電壓仍為負值（-Frfc/2)，所以第一電感電流 Lpi持續線性下降。由於設計轉換器工作於DCM，所以第 • 電感電流Lpl會在藤動訊號Fgd變為低電位前先遞減到 . 零’當第一電感電流下降到零即進入工作模式V。 (5) 工作模式iV-b : 工作模式IV-b是發生於輸入電壓在較低電壓時，此時， 第一電感電流已於工作模式III時先降為零，且h為正 131001.doc •16· 201010497 值並流經1)2。因此，當&振盡經過零點變為負值時鳴截 止，該第二切換開關⑽之切換導通進入工作模式V。 (6)工作模式v : 進入工作模式V的瞬間H切換開關導通㈣ 負值並流經該第二切換開關仏，此時諧振迴路從第二電容 c2汲取能量。當由高電位變為低電位時該第二切換 開關Q2截止，電路則進人下—個高頻週期的卫作模式】。 因此’不論從在工作模式職人模式IV a，或是從工作 模式入模式IV_b，再到模式Ve在該第二切換開關Q2 導通之則，為正值且流經D2，Q2兩端所跨電壓幾乎為 零’因此’該第二切換開關匕可達成零電堡切換導通。由 上述工作模式分析可發現，該第一切換開關Qi及該第二切 換開關Q2均具有零電壓切換導通的優點，可以大幅度降低 切換損失。因Λ ’本發明之單級具零電壓切換之㈣驅動 電路具高功因，高電路效率及具有減少電路元件與降低成 本之功效。 參考圖6，其顯示本發明單級具零電壓切換之led驅動 電路第四實施例之電路示意圖。在本發明第二實施例單級 具零電壓切換之LED驅動電路60中，該功因修正電路係為 降升壓式功因修正電路，該隔離式轉換器係為隔離式準半 橋諧振轉換器。與第三實施例不同之處在於，第二實施例 單級具零電壓切換之LED驅動電路60不具有第二電容^。 且該第三整流二極體D3連接於該第一整流二極體Dfi及該 第二切換開關Q2與該第一電容Cl之並聯連接點之間，該第 131001.doc •17- 201010497 四整流二極體D4連接於該第二整流二極體Df2及該第一切 換開關Ql與該第一電容之並聯連接點之間。因此，第四 實施例單級具零電麼切換之LED驅動電路60具有第三實施 例單級具零電壓切換之LED驅動電路5〇之功效。 本發明之單級具零電壓切換之LED驅動電路另包括一控 制電路（圖未示出），用以控制該切換開關之導通與否。 本發明之單級具零電壓切換之LED驅動電路將功因修正 φ 電路與隔離式轉換器進行整合，隔離式轉換器内之部分元 件與功因修正電路之部分元件相同。功因修正電路之電感 工作於不連續導通模式（DCM)之下，可使功率因數接近 1。且該隔離式轉換器工作於電感性負載模式之下，使所 有的主動開關均具有零電壓切換（zvs)導通的優點，降低 主動開關的切換損失。因此，本發明之單級具零電壓切換 之LED驅動電路具高功因、高電路效率及具有減少電路元 件與降低成本之功效。 參惟上述實施例僅為說明本發明之原理及其功效，而非限 制本發明。因此，習於此技術之人士對上述實施例進行修 改及變化仍不脫本發明之精神。本發明之權利範圍應如後 述之申請專利範圍所列。 【圖式簡單說明】 圖1顯示習知LED驅動電路之方塊示意圖； 圖2顯示本發明之單級具零電壓切換之lEd驅動電路之 方塊示意圖； 圖3顯示本發明單級具零電壓切換之lEd驅動電路第一 131001.doc -18- 201010497 實施例之電路示意圖； 圖4顯示本發明單級具零電壓切換之LED驅動電路第二 實施例之電路示意圖； 圖5顯示本發明單級具零電壓切換之LED驅動電路第三 實施例之電路示意圖； 圖6顯示本發明單級具零電壓切換之LED驅動電路第四 實施例之電路示意圖。 【主要元件符號說明】 10 習知LED驅動電路 11 被動遽波器 12 前級功因修正電路 13 後級多繞組輸出隔離式轉換器 14 LED組 21 被動濾波器 22 本發明之單級具零電壓切換之 LED驅動電路 24 LED組 30 本發明第一實施例單級具零電壓 切換之LED驅動電路 40 本發明第二實施例單級具零電壓 切換之LED驅動電路 50 本發明第三實施例單級具零電壓 切換之LED驅動電路 60 本發明第四實施例單級具零電壓 131001.doc -19- 201010497[5] Zhou Zhimin, Zhou Jihai, Ji Aihua, 屦鸢f*路设#/舆推荐, Shanghai Post and Telecommunications Press, 2006. SUMMARY OF THE INVENTION The present invention provides a single-stage LED driving circuit with zero voltage switching, including: a power factor correction circuit and an isolated converter with zero voltage switching. The power factor correction circuit is configured to receive an AC input voltage to correct the cause of the 131001.doc 201010497. The isolated converter with zero voltage switching is connected to the power factor correction circuit 'which has at least one switch, the switch-on relationship is zero voltage switching'. The isolated converter is used to convert the AC input voltage into at least a DC output voltage. To drive at least one LED. The single-stage LED driving circuit with zero voltage switching of the present invention integrates the power correction circuit and the isolated converter, and some components in the isolated converter are identical to some components of the power factor correction circuit. The inductance of the power correction circuit ❿ operates in the Discontinuous conduction mode (DCM) to make the power factor close to 丨. And the isolated converter operates under inductive load mode, so that all active switches have the advantage of zero voltage switching (ZVS) conduction, reducing the switching loss of the active switch. Therefore, the single-stage LED driving circuit with zero voltage switching of the present invention has high power factor, high circuit efficiency, and has the effects of reducing circuit components and reducing cost. [Embodiment] Φ Referring to Fig. 2', there is shown a schematic diagram of a single-stage lEd medium circuit with zero voltage switching of the present invention. The single stage zero voltage switching led drive circuit 22 of the present invention comprises: a power factor correction circuit 221 and a zero voltage switching isolation converter 222. The power factor correction circuit 22 is configured to receive an AC input - voltage ' to correct the power factor. The zero-voltage switching isolated converter 222 is connected to the power factor correction circuit, which has at least one switch, the switch-on relationship is zero voltage switching. The isolated converter is used to convert the AC input voltage into at least a continuous current. Output voltage to drive at least one [ΕΕ]. In the embodiment of the present invention, the zero-voltage switching isolated converter 222 can be a 131001.doc 201010497 isolated converter with multiple winding outputs and zero voltage switching to provide a plurality of DC output voltages to drive multiple groups. Or a multi-color LED 24, the LED group 24 includes a red LED 241, a green LED 242, and a blue LED 243. The single-stage zero voltage switching LED driving circuit 22 of the present invention further includes a passive filter 21 for filtering high frequency components, and the passive filter 21 is connected between the alternating current input voltage and the power factor correcting circuit 221. Referring to Figure 3', there is shown a circuit diagram of a first embodiment of a single-lead LED drive φ circuit with zero voltage switching of the present invention. In the single-stage zero-voltage switching LED driving circuit 30 of the first embodiment of the present invention, the power factor correcting circuit is a boosting power factor correcting circuit, and the isolated converter is an isolated positive half-bridge resonant converter. . The passive filter includes a filter inductor Lf and a filter capacitor Cf. The power correction circuit includes: a first rectifying diode DDR, a second rectifying diode Dr2, a first inductor, a first switching switch, a second switching switch Q2, a first capacitor q and a a second capacitor c2; wherein the first rectifying diode Dri is connected to the second rectifying diode Dr2; the first switching switch Q! is connected to the second switching switch A, and the first rectifying diode The body Dri and the first rectifying __ pole body Dr2 are connected in parallel; the __capacitor c ^ is connected to the second capacitor C2, and is connected in parallel with the first switching switch 仏 and the second switching switch Q2 The first inductor L! is connected between the passive filter and a connection point a between the first switch 仏 and the second switch A. The isolated converter with zero voltage switching includes: the first switching switch Qi, the second switching switch Q2, the first capacitor Ci, the second capacitor C2, a third capacitor Cr, a third inductor Lr, A transformer τ and a rectifier R. 131001.doc •9- 201010497 The single-stage led-drive circuit with zero voltage switching of the present invention integrates the power correction circuit and the isolated converter, and some components and power correction circuits in the isolated converter In the embodiment, the first switch Q1, the second switch Q2, the first capacitor q, and the second capacitor c2 of the isolated converter with zero voltage switching are connected to the work. The first switching switch Qi, the second switching switch q2, the first capacitor and the second capacitor c2 of the correction circuit are the same. φ In the present embodiment, the third capacitor cr and the third inductor Lr are connected, and are connected to the first switch Q, and the connection point a of the second switch Q2; the transformer T is connected to the third The inductor Lr and a connection point b between the first capacitor Ci and the second capacitor C2; the rectifier r is connected to the transformer τ. The rectifier R includes four rectifying diodes Dr5, Df6, Da, and Du. The transformer T can be a multi-winding output transformer to provide a plurality of DC output voltages to drive a plurality of LEDs. The following describes the working mode of the single-stage lEd drive driving circuit with zero voltage switching in the first embodiment of the present invention: (1) Working mode I: When the driving signal Fgi; 2 turns off the second switching switch q2, it enters the work. Mode I. After a short delay time, the driving signal 匕s1 of the first switching switch changes from a low potential to a high potential, and the first switching switch Qi • is not turned on immediately. Since the resonant circuit is designed to be inductive, the resonant current h will lag behind the voltage, so at the instant when the second switch A is turned off, ^ is a negative value and flows backward through the diode (available) - The pole between the bungee is used as the 仏 and ]^, and the additional parallel diode p is required. Once the 131001.doc 10-201010497 D! turns on the rectified input voltage across the __inductor Q, the inductor The current / η increases linearly from zero, and the rate of increase of L is proportional to the voltage of the wheel. At first, Zil is smaller than '... and the resultant current is still reversed, and Di continues to conduct. Prepare! £1 rises to make /si turn to In the forward direction, D! wears the first switch Q, and then turns on, and enters the working mode. Because the first switch-switch QA is turned on, the electric (four) is zero, which has the advantage of zero voltage switching conduction, which greatly reduces the Switching loss. ^ (2) Working mode II: When the first switching switch Q1 is turned on, the voltage across the first inductor is still equal to the rectified input voltage, the inductor current ^ continues to increase linearly, and the spectral current (4) From a negative value to a positive value. "A positive value, h and, · And flowing through the first switching switch Qi. When the first switching switch Qi is turned off, the inductor current h reaches the peak value of the cycle, and then enters the working mode ΠΙ. (3) Working mode ΠΙ: • when it enters the working mode m , & is positive, the current path is converted by the first switch Q! to the diode A, and the second capacitor is charged. On the other hand, the inductor current h flows through D2 while the first capacitor q. The second capacitor 〇 is charged. The voltage OMM of the first inductor A is negative, ... linearly decreases from the value of 2. In order to make the converter operate in DCM, the first electric valley and the second capacitor C2 The voltage at both ends and (6) must be greater than twice the peak value of the AC input voltage “5.” Since the peak value of h is proportional to the AC input voltage ~, the time that the heart drops to zero varies with the input voltage. Late falls to 131001.doc -11 - 201010497 zero, enters working mode IV-a; conversely, when... drops to zero earlier than g then enters working mode IV-b » (4) Operating mode IV-a: When AC input voltage Vs at a higher voltage, oscillates to zero and then reverses, at this time The inductor current h continues to decrease linearly. When G re-oscillates to "large", the second switch Q2 is turned on, and the difference between the & and the heart flows through the second switch Q2. The drive signal becomes low. Previously, the inductor current will first drop to zero and then enter the operating mode v. (5) Operating mode IV-b: When the AC input voltage v, at a lower voltage, 仏 will first drop to zero, the power supply stops input current At this time, '^ is still positive and continues to flow through D2 until the k-oscillation passes through the zero point and becomes a negative value. The second switch 匕 turns on with the turn-off switch and then enters the operating mode V. (6) Working mode V: At this time, the second switching switch Q2 is turned on, Ζ·Λ is negative and flows through the second switching ❹ switch Q2, and the second capacitor Q supplies energy to the resonant circuit, when ~s2 is changed from high potential At the moment of low potential, the second switch A is loaded and the circuit returns to the operating mode I of the next high frequency period. Therefore, whether it enters mode 1¥_& in working mode πι, or enters mode gray-b from working mode III, then goes to mode V. When the second switch Q2 is turned on, h is a positive value and flows through 〇2, and the voltage across Q2 is almost zero. Therefore, the second switch Q2 can achieve zero voltage switching conduction. It can be found from the above working mode that the first switching switch Q1 and the second switching switch Q2 have the advantages of zero voltage switching conduction, and can greatly reduce the switching loss of 131001.doc -12-201010497. Therefore, the single-stage LED driving circuit with zero voltage switching of the present invention has high power factor, high circuit efficiency, and the effect of reducing circuit components and reducing cost. Referring to Figure 4, there is shown a circuit diagram of a second embodiment of a single stage zero voltage switching LED drive circuit of the present invention. In the LED driving circuit 40 of the single-stage zero-voltage switching of the second embodiment of the present invention, the power factor correcting circuit is a boosting power factor correcting circuit, and the isolated converter is an isolated quasi-half bridge resonant conversion. Device. The difference from the first embodiment is that the LED driving circuit 40 of the second embodiment having zero voltage switching has no second capacitance c2. Therefore, the single-stage single-voltage zero-voltage switching Led driving circuit 40 of the second embodiment has the effect of the LED driving circuit 3 of the single-stage zero voltage switching of the first embodiment. Referring to Figure 5, there is shown a circuit diagram of a third embodiment of a single stage zero voltage switching lED driver circuit of the present invention. In the LED driving circuit 50 of the single-stage zero voltage switching of the third embodiment of the present invention, the power factor correcting circuit is a step-down power factor correcting circuit, and the isolated converter is an isolated positive half φ bridge resonance. converter. The power correction circuit includes: a first rectifying diode DDR, a second rectifying diode Dr2, a third rectifying diode D3, a fourth rectifying diode D4, a first inductor Lpl, and a first a second inductor Lp2, a first switching switch Qi, a second switching switch Q2, a first capacitor and a second capacitor C2; wherein the first rectifying diode DDR is connected to the second rectifying diode Dr2 The first switch Q is connected to the second switch q2; the first capacitor G is connected to the second capacitor C2, and is connected in parallel with the first switch (^ and the second switch Q2; An inductor [^ is connected between the first rectifying diode 131001.doc • 13· 201010497 body Dr1 and the first switching switch Q]; the second inductor Lp2 is connected to the second rectifying diode Du and the first The second rectifier diode D3 is connected to the fourth rectifier diode D4, and is connected in parallel with the first rectifier diode Dr1 and the second rectifier diode Dr2. The isolated converter with zero voltage switching includes: the first switch Q!, the second switch Q2, the first a capacitor C, a second capacitor C2, a second capacitor cr, a third inductor Lr, the third rectifying diode d3, the φ fourth rectifying diode D4, a transformer T and a rectifier R. The invention The single-stage LED drive circuit with zero voltage switching integrates the power correction circuit and the isolated converter, and some components in the isolated converter are identical to some components of the power correction circuit. In this embodiment, The first switching switch Q] having the zero-voltage switching isolator, the second switching switch Q2, the third rectifying diode D3, the fourth rectifying diode d4, the first capacitor C! The second capacitor c2 is coupled to the first switching switch Q! of the power factor correction circuit, the second switching switch Q2, the third rectifier diode 〇3, the Qth rectifying diode 鳢d4, and the second capacitor A capacitor q and the second capacitor C2 are the same. In this embodiment, the third capacitor Cr and the third inductor Lr are connected, and are connected to the first switch 仏 and the second switch () 2 Point a; the transformer T is connected to the third inductor Lr and the first capacitor C, and the second capacitor Between the connection point b of C2; the rectifier R is connected to the transformer T. The rectifier comprises four rectifying diodes Dr5, Dr6, Dr7 and Dr8. The transformer can be a multi-winding output transformer to provide a plurality of DC output voltages Driving a plurality of LEDs. The following describes a single-stage LED drive with single voltage switching of the third embodiment of the present invention. 131001.doc • 14· 201010497 The working mode of the dynamic circuit: (1) Working mode I: When the driving signal 匕 2 When the second switch Q2 is turned off, the operation mode I is entered. After a short delay time, the driving signal h of the _th switching (4) is changed from a low level to a high level, and the first switching is not immediately performed. Turn on. Since the resonant circuit is designed to be inductive, the resonant current b will lag behind the voltage, so at the instant when the second switching switch Q2 is turned off, G ❹ is a negative value and flows backward through the diode D (the base MOSFET of the MOSFET can be utilized) The first one is used as the 仏 and D2, and the additional parallel diode p is turned on. Once the rectified input voltage is across the first inductor Lpi, the inductor current increases linearly from zero, increasing the speed and input voltage. In the beginning, ζζρ1 is smaller, "...and the composite current h of the heart is still reversed, 〇! Continue to conduct. When h rises to make /si turn to positive, the first switch is turned on, Enter the working mode〗. Because the first switch (^ voltage is equal to zero when switching on, the advantage of zero voltage switching conduction is greatly reduced, and the switching loss is greatly reduced. (2) Working mode II: At the moment of entering working mode II, The first switch Q is turned on, the voltage across the first inductor is still equal to the rectified input voltage, the inductor current Upl continues to increase linearly, and the resonant current & gradually oscillates from a negative value to a positive value. After 正 is positive, 'Qpl and the heart flow through the first switch Q!. When the driving voltage Fg5l turns to the low level, the first switch (^ cutoff 'inductor current Qpl reaches the peak of this period, then Enter working mode III. 13ia01.doc -15- 201010497 (3) Working mode Hi: "To make the converter work in DCM, the first capacitor C must be designed! Both ends, (4) M (^/2) is greater than AC input power The peak value of & causes the first rectifying body 220r to be reverse biased. At this time, the first inductor current center i will no longer flow through the input power source, but flow through the third rectifying diode 〇3, and Charging the first capacitor 。. Since the voltage across the first inductor is negative (_ 匕 c/2) 'the first inductor current core linearly decreases from the peak value. And because the φ-th inductor current The peak value of ...1 is proportional to the input voltage v, so the time during which the first inductor current ζΖρ1 drops to zero varies with the change of the input voltage 〜. If the first inductor current falls to zero later, it enters the operating mode IV- a, conversely, when the first inductor current drops to zero earlier than & Entering the working mode IV-b. When the working mode is entered, the current path of & is converted from the first switching switch Q1 to the diode d2, and the second capacitor c2 is charged. Operating mode iv-a: φ Operating mode 1V-a occurs when the input voltage is at a higher voltage. At this time, the second switching switch Q2 is turned on, and the second switching switch G flows through Q2. The terminal voltage is still negative (-Frfc/2), so the first inductor current Lpi continues to decrease linearly. Since the converter is designed to operate in DCM, the inductor current Lpl will be decremented before the Fujin signal Fgd goes low. To zero. When the first inductor current drops to zero, it enters the operating mode V. (5) Operating mode iV-b: Operating mode IV-b occurs when the input voltage is at a lower voltage. At this time, the first inductor current has first dropped to zero in the operating mode III, and h is positive 131001.doc •16· 201010497 The value flows through 1)2. Therefore, when the & vibration is turned off and the zero point becomes a negative value, the switching of the second switching switch (10) is turned on to enter the operation mode V. (6) Operation mode v: At the instant of entering the operation mode V, the H switch is turned on (4) and flows through the second switch 仏, at which time the resonant circuit draws energy from the second capacitor c2. When the high potential is changed to the low level, the second switching switch Q2 is turned off, and the circuit enters a lower-frequency mode of the high frequency period. Therefore, whether it is from the working mode staff mode IV a, or from the working mode to the mode IV_b, and then the mode Ve is turned on in the second switching switch Q2, it is positive and flows through D2, the voltage across Q2 Almost zero 'so' the second switch 匕 can achieve zero electric switch switching conduction. It can be found from the above operation mode that the first switching switch Qi and the second switching switch Q2 have the advantages of zero voltage switching conduction, and the switching loss can be greatly reduced. The single-stage zero-voltage switching (four) driving circuit of the present invention has high power factor, high circuit efficiency, and has the effects of reducing circuit components and reducing cost. Referring to Figure 6, there is shown a circuit diagram of a fourth embodiment of a single stage LED drive circuit with zero voltage switching. In the LED driving circuit 60 of the single-stage zero voltage switching of the second embodiment of the present invention, the power factor correcting circuit is a step-down power factor correcting circuit, and the isolated converter is an isolated quasi-half bridge resonant converter. Device. The difference from the third embodiment is that the single-stage LED drive circuit 60 with zero voltage switching does not have the second capacitor. The third rectifying diode D3 is connected between the first rectifying diode Dfi and the parallel connection point of the second switching switch Q2 and the first capacitor C1, the 131001.doc • 17- 201010497 four rectification The diode D4 is connected between the second rectifying diode Df2 and the parallel connection point of the first switching switch Q1 and the first capacitor. Therefore, the LED driving circuit 60 of the single-stage zero-voltage switching of the fourth embodiment has the effect of the LED driving circuit 5 of the single-stage zero-voltage switching of the third embodiment. The single-stage zero voltage switching LED driving circuit of the present invention further includes a control circuit (not shown) for controlling whether the switching switch is turned on or not. The single-stage LED driving circuit with zero voltage switching of the present invention integrates the power factor correction φ circuit and the isolated converter, and some components in the isolated converter are identical to some components of the power factor correction circuit. The inductance of the power correction circuit operates in discontinuous conduction mode (DCM), which makes the power factor close to 1. And the isolated converter operates in inductive load mode, so that all active switches have the advantage of zero voltage switching (zvs) conduction, reducing the switching loss of the active switch. Therefore, the single-stage LED driving circuit with zero voltage switching of the present invention has high power factor, high circuit efficiency, and has the effects of reducing circuit components and reducing cost. The above examples are merely illustrative of the principles of the invention and its effects, and are not intended to limit the invention. Therefore, those skilled in the art can make modifications and changes to the above embodiments without departing from the spirit of the invention. The scope of the invention should be as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a conventional LED driving circuit; FIG. 2 is a block diagram showing a single-stage zero-voltage switching lEd driving circuit of the present invention; FIG. 3 is a view showing a single-stage zero voltage switching of the present invention. lEd drive circuit first 131001.doc -18- 201010497 embodiment circuit diagram; FIG. 4 shows a schematic diagram of a second embodiment of the single-stage zero voltage switching LED drive circuit of the present invention; FIG. 5 shows the single stage zero of the present invention FIG. 6 is a circuit diagram showing a fourth embodiment of the LED driving circuit of the single-stage zero voltage switching of the present invention. FIG. [Main component symbol description] 10 Conventional LED driver circuit 11 Passive chopper 12 Pre-stage power factor correction circuit 13 Rear stage multi-winding output Isolated converter 14 LED group 21 Passive filter 22 Single-stage zero voltage of the present invention Switching LED drive circuit 24 LED group 30 The first embodiment of the present invention has a single-stage zero voltage switching LED drive circuit 40. The second embodiment of the present invention has a single-stage zero voltage switching LED drive circuit 50. LED drive circuit 60 with zero voltage switching of the stage. The fourth embodiment of the present invention has a single voltage of zero voltage 131001.doc -19- 201010497
切換之LED驅動電路 141 紅色LED 142 綠色LED 143 藍色LED 221 功因修正電路 222 具零電壓切換之隔離式轉換器 241 紅色LED 242 綠色LED 243 藍色LED Ci 第一電容 c2 第二電容 cr 第三電容 Cf 濾波電容 Drl 第一整流二極體 Dr2 第二整流二極體 Di、D2 基底-汲極間的二極體 d3 第三整流二極體 d4 第四整流二極體 Li 第一電感 Lp 1 第一電感 Lp2 第二電感 Lr 第三電感 Lf 濾波電感 Qi 第一切換開關 131001.doc -20- 201010497Switching LED Driver Circuit 141 Red LED 142 Green LED 143 Blue LED 221 Power Correction Circuit 222 Isolated Converter with Zero Voltage Switching 241 Red LED 242 Green LED 243 Blue LED Ci First Capacitor c2 Second Capacit Cr Three capacitor Cf filter capacitor Drl first rectifier diode Dr2 second rectifier diode Di, D2 base-drain diode di3 third rectifier diode d4 fourth rectifier diode Li first inductor Lp 1 First inductance Lp2 Second inductance Lr Third inductance Lf Filter inductance Qi First switching switch 131001.doc -20- 201010497
q2 第二切換開關 τ 變壓器 R 整流器 Dr5、Dr6、Dr7、Dr8 四個整流二極體 -21- I31001.docQ2 Second switch τ Transformer R rectifier Dr5, Dr6, Dr7, Dr8 four rectifier diodes -21- I31001.doc