201233249 六、發明說明： 【發明所屬之技術領域】 [0001] 本發明涉及背光源驅動系統，特別涉及一種多燈管驅動 系統。 【先前技術】 [0002] 冷陰極螢光燈常用作液晶顯示幕的背光源。為驅動冷陰 極螢光燈點亮，需要逆變器將直流電源轉換為交流電源 ，提供合適的驅動電源。為保護冷陰極螢光燈及逆變器 本身，逆變器中常設置異常偵測及保護電路，以及時偵 測異常並採取保護措施。通常，異常偵測及保護電路將 偵測到的訊號與設定的參考電壓進行比較，來確定是否 進行保護。然而，因設定的參考電壓為固定電壓，容易 因環境溫度及燈管參數變化而導致保護誤動作。 【發明内容】 [0003] 有鑑於此，需提供一種多燈管驅動系統，能精確偵測異 常，避免誤動作。 [0004] 一種多燈管驅動系統，用於驅動複數燈管，包括濾波電 路、開關電路、脈衝寬度調變控制器、保護電路、複數 變壓器及異常偵測電路。每一變壓器包括初級繞組及次 級繞組，該等變壓器的初級繞組並聯連接該開關電路， 該等變壓器的次級繞組的高壓端一一對應連接該等燈管 。異常偵測電路連接該變壓器及該保護電路，用於偵測 該多燈管驅動系統及該等燈管是否異常，包括訊號轉換 電路、最高管電流取得電路、最低管電流取得電路及比 較電路。訊號轉換電路連接該等變壓器的次級繞組的低 100103053 表單編號A0101 第4頁/共20頁 1002005413-0 201233249 Ο 壓端，用於將流經該等燈管的電流訊號轉換為電壓訊號 。最高管電流取得電路連接該訊號轉換電路，用於取得 該等燈管中電流最高的燈管轉換後的最高電壓訊號。最 低管電流取得電路連接該訊號轉換電路，用於取得該等 燈管中電流最低的燈管轉換後的最低電壓訊號。比較電 路連接該最高管電流取得電路及該最低管電流取得電路 ，用於比較該最高電壓訊號與該最低電壓訊號的差值是 否超過預先設定範圍，及在該最高電壓訊號與該最低電 壓訊號的差值超過該預先設定範®時，產生觸發訊號。 其中，該保護電路在接收到該觸發訊號時，控制該脈衝 寬度調變控制器停止輸出脈衝寬度調變訊號，從而關閉 該開關電路的輸出。 [0005] Ο [0006] 優選地，該訊號轉換電路包括複數訊號轉換單元，—— 對應連接該等變壓器的次級繞組的低壓端，每一訊號轉 換單元包括第一電阻及第一電容，該第一電阻一端連接 對應的變壓器的次級繞組的低壓端，另一端接地，該第 一電容與該第一電阻並聯。 優選地，該最高管電流取得電路包括複數第一二極體， ——對應連接該訊號轉換單元與該等變壓器的次級繞組 的低壓端，陽極分別連接對應的變壓器的次級繞組的低 壓端，陰極相連並輸出該最高電壓訊號。 [0007] 優選地，該最低管電流取得電路包括複數第二二極體， ——對應連接該訊號轉換單元與該等變壓器的次級繞組 的低壓端，陰極分別連接對應的變壓器的次級繞組的低 壓端，陽極相連且經由第二電阻接收第一參考電壓並輸 100103053 表單編號Α0101 第5頁/共20頁 1002005413-0 201233249 出該最低電壓訊號。 [0008] 優選地，該比較電路包括開關、第三二極體、第二電容 及第四電阻。開關包括控制極、第一電極及第二電極， 該控制極連接該等第二二極體的陽極並經由第三電阻接 地，該第一電極連接該等第一二極體的陰極。該第三二 極體的陽極連接該開關的第二電極，陰極輸出該觸發訊 號。第二電容的一端連接該第三二極體的陰極，另一端 接地。第四電阻與該第二電容並聯。 [0009] 優選地，該開關為P型金屬氧化物半導體場效應管，該控 制極為閘極，該第一電極為源極，該第二電極為汲極。 [0010] 優選地，該比較電路包括比較器、第三二極體、第二電 容、第四電阻及第五電阻。比較器包括正輸入端、負輸 入端及輸出端，該正輸入端連接該等第一二極體的陰極 ，該負輸入端連接該等第二二極體的陽極。該第三二極 體的陽極連接該比較器的輸出端，陰極輸出該觸發訊號 。第二電容的一端連接該第三二極體的陰極，另一端接 地。第四電阻與該第二電容並聯。第五電阻一端連接該 比較器的輸出端，另一端接收第二參考電壓。 [0011] 上述多燈管驅動系統動態取得最高管電流與最低管電流 並進行比較，以確定是否發生異常，因而，當環境溫度 及燈管參數變化時，最高管電流與最低管電流均隨之變 化，不會影響異常狀況的判斷，避免誤動作的產生。 【實施方式】 [0012] 圖1為本發明一實施方式中多燈管驅動系統10的示意圖。 100103053 表單編號A0101 第6頁/共20頁 1002005413-0 201233249 Ο 在本實施方式中，多燈管驅動系統10用於將輸入電源Vin 轉換為交流電源，驅動複數燈管LI、L2 (僅以兩個為例 )。其中，輸入電源Vin為直流電源。在本發明的其它實 施方式中，輸入電源V i η也可為交流電源。多燈管驅動系 統1 0包括濾波電路1 00、開關電路120、脈衝寬度調變控 制器110、複數變壓器ΤΙ、Τ2、異常偵測電路130及保護 電路140。濾波電路100用於濾波，在本實施例中，濾波 電路10 0包括電容，例如，三個相互並聯的電容。濾波電 路100濾波後輸出直流電源訊號。開關電路120與濾波電 路100相連，用於將濾波電路100輸出的直流電源訊號轉 換為第一交流電源訊號。在本實施方式中，第一交流電 源訊號為方波訊號。開關電路120包括全橋電路、半橋電 路、推挽式電路等。 [0013] Ο 脈衝寬度調變控制器110用於產生脈衝寬度調變訊號，控 制開關電路120導通或關閉，從而將濾波電路100輸出的 直流電源訊號轉換為第一交流電源訊號。保護電路140用 於在多燈管驅動系統10或燈管LI、L2異常時，進行保護 ，並通知脈衝寬度調變控制器110，使脈衝寬度調變控制 器110停止輸出脈衝寬度調變訊號，開關電路120停止轉 換，從而使多燈管驅動系統10關掉，避免損壞。 [0014] 每一變壓器ΤΙ、Τ2均包括初級繞組與次級繞組。變壓器 ΤΙ、Τ2的初級繞組並聯連接開關電路120，次級繞組的高 壓端——對應連接燈管LI、L2，即變壓器Τ1的次級繞組 的高壓端對應連接燈管L1，變壓器Τ2的次級繞組的高壓 端對應連接燈管L2。變壓器ΤΙ、Τ2用於將開關電路120 100103053 表單編號Α0101 第7頁/共20頁 1002005413-0 201233249 輸出的第一交流電源訊號轉換為第二交流電源訊號。在 本實施方式中，第二交流電源訊號為弦波訊號。 [0015] 異常偵測電路130連接變壓器ΤΙ、T2及保護電路140，用 於偵測多燈管驅動系統10及燈管LI、L2是否異常，包括 訊號轉換電路1 300、最高管電流取得電路1310、最低管 電流取得電路1 320及比較電路1 330。訊號轉換電路1300 連接變壓器ΤΙ、T2的次級繞組的低壓端，用於將流經燈 管LI、L2的電力訊號轉換為電壓訊號。最高管電流取得 電路1310連接訊號轉換電路1300，用於取得燈管LI、L2 中電流最高的燈管轉換後的最高電壓訊號。最低管電流 取得電路1 320連接訊號轉換電路1 300，用於取得燈管L1 、L2中電流最低的燈管轉換後的最低電壓訊號。比較電 路1 330連接最高管電流取得電路1310及最低管電流取得 電路1 320，用於比較最高電壓訊號與最低電壓訊號的差 值是否超過預先設定範圍，及在該最高電壓訊號與最低 電壓訊號的差值超過預先設定範圍時，產生觸發訊號， 觸發保護電路140。在本實施方式中，預先設定範圍可根 據實際情況及需要設定，例如，為0. 7V。保護電路140在 接收到該觸發訊號時，進行保護，並控制脈衝寬度調變 控制器110停止輸出脈衝寬度調變訊號，從而關閉開關電 路120的輸出。 [0016] 多燈管驅動系統1 0動態取得最高管電流與最低管電流並 進行比較，以確定是否發生異常，取代了傳統的固定參 考電壓比較，因而，環境溫度及燈管LI、L2參數變化時 ，最高管電流與最低管電流均隨之變化，避免誤動作的 100103053 表單編號A0101 第8頁/共20頁 1002005413-0 201233249 產生。此外，在對多燈管驅動系統1 0進行安規要求項目 ，如接觸電流，測試時，燈管LI、L2被短路使得燈管L1 、L2的電容不參與諧振，而導致管電流訊號產生相移， 異常偵測電路130可偵測到此異常並觸發保護電路140。 [0017] ❹ Ο [0018] 圖2所示為本發明一實施方式中多燈管驅動系統1 0的電路 圖。在本實施方式中，訊號轉換電路1300包括複數訊號 轉換單元1301，——對應連接變壓器ΤΙ、T2的次級繞組 的低壓端，即第一個訊號轉換單元1301連接變壓器T1， 第二個訊號轉換單元1301連接變壓器T2。每一訊號轉換 單元1301用於將對應的燈管LI、L2的電流訊號轉換為電 壓訊號，其包括第一電阻K1及第一電容C1。第一電阻R1 的一端連接對應的變壓器ΤΙ、T2的次級繞組的低壓端， 另一端接地，第一電容C1與第一電阻R1並聯。其中，第 一電阻R1用於將對應的燈管LI、L2的電流訊號轉換為電 壓訊號，第一電容C1用於對第一電阻R1轉換後的電壓訊 號濾波，以取得穩定電壓。在本實施方式中，轉換後的 電壓訊號為交流訊號。 最高管電流取得電路1310包括複數第一二極體D1，一一 對應連接訊號轉換單元1301與變壓器ΤΙ、T2的次級繞組 的低壓端。該等第一二極體D1的陽極分別連接對應的變 壓器ΤΙ、T2的次級繞組的低壓端，陰極相連並輸出最高 電壓訊號。該等第一二極體D1將訊號轉換單元1301轉換 後的電壓訊號中的最高電壓訊號篩選並輸出至比較電路 1330。 [0019] 最低管電流取得電路1 320包括複數第二二極體D2，—— 100103053 表單編號A0101 第9頁/共20頁 1002005413-0 201233249 對應連接訊號轉換單元1301與變壓器ΤΙ、T2的次級繞組 的低壓端。該等第二二極體D2的陰極分別連接對應的變 壓器ΤΙ、Τ2的次級繞組的低壓端，陽極相連且經由第二 電阻R2接收第一參考電壓Vccl並輸出最低電壓訊號至比 較電路1330。在本貫施方式中*最向電壓訊號與最低電 壓訊號均為交流訊號。 [0020] 比較電路1 330包括開關Q、第三二極體D3、第三電阻R3 、第二電容C2及第四電阻R4。開關Q包括控制極、第一電 極及第二電極。開關Q的控制極連接第二二極體D2的陽極 ，即接收最低電壓訊號，並經由第三電阻R3接地。開關Q 的第一電極連接第一二極體D1的陰極，即接收最高電壓 訊號，第二電極連接第三二極體D3的陽極。第三二極體 D3的陰極輸出該觸發訊號至保護電路。第二電容C2的一 端連接第三二極體D3的陰極，另一端接地。第四電阻R4 與第二電容C2並聯。第三二極體D3、第二電容C2及第四 電阻R4用於將交流的最高電壓訊號轉換為直流訊號，然 後輸出至保護電路140，即觸發訊號為直流訊號。 [0021] 在本實施方式中，開關Q為P型金屬氧化物半導體場效應 管，控制極為閘極，第一電極為源極，第二電極為汲極 〇 [0022] 在本實施方式中，燈管LI、L2的參數相同，變壓器T1、 T2的參數相同，訊號轉換單元1301的參數相同，第一二 極體D1的參數相同，第二二極體D2的參數相同。因而， 若燈管LI、L2及多燈管驅動系統10無異常，流經燈管L1 、L2的電流相差不大，差異值未達到預先設定範圍，比 100103053 表單編號A0101 第10頁/共20頁 1002005413-0 201233249 較電路1 330無觸發訊號產生，保護電路140不會進行保護 〇 [0023] Ο [0024] 若燈管LI、L2及多燈管驅動系統10中任一者異常，例如 ，燈管L1斷管，此時，流經燈管L1的電流很小。因而， 與燈管L1對應的訊號轉換單元1301的電壓訊號的電壓小 於與燈管L2對應的訊號轉換單元1301的電壓訊號的電壓 。又因為第一二極體D1參數相同，陰極相連，故與燈管 L2對應的第一二極體導通，即，第一二極體D1取得與最 高電流訊號對應的最高電壓訊號。開關Q的第一電極的電 壓等於最高電壓訊號減去第一二極體D1的導通壓降。 Ο 同時，因為第二二極體D2參數相同，陽極相連，故與燈 管L1對應的第二二極體D2導通，即，第二二極體D2取得 與最低電流訊號對應的最低電壓訊號。開關Q的控制極的 電壓等於最低電壓訊號加上第二二極體D2的導通壓降。 開關Q的控制極與第一電極的壓差為最低電壓加上第一二 極體D1與第二二極體D2的導通壓降再減去最高電壓，因 為最低電壓幾乎為0，最高電壓至少為幾伏，開關Q導通 。此時，最高電壓訊號輸入至第三二極體D3的陽極，經 第三二極體D3、第二電容C2及第四電阻R4的整流濾波後 ，變成直流形式的觸發訊號，並輸入至保護電路140。如 此，偵測電路130可偵測出異常。 [0025] 圖3所示為本發明另一實施方式中多燈管驅動系統20的電 路圖。本實施方式中的多燈管驅動系統2 0與圖2中的多燈 管驅動系統10的區別在於比較電路1 330Α的具體架構不同 於比較電路1330，其餘部分完全相同，因而此處不再贅 100103053 表單編號Α0101 第11頁/共20頁 1002005413-0 201233249 述。比較電路1 330A包括比較器1331、第三二極體D3、 第二電容C2、第四電阻R4及第五電阻R5。比較器1 331的 正輸入端連接第一二極體D1的陰極，負輸入端連接第二 二極體D2的陽極，輸出端連接第三二極體D3的陽極。第 五電阻R5的一端連接比較器1331的輸出端，另一端接收 第二參考電壓。第三二極體D3、第二電容C2及第四電阻 R4的連接關係與作用與圖2中的相同，此處不再詳述。在 本實施方式中，比較電路1 330A與圖2中的比較電路1330 的區別在於用比較器1331取代開關Q，但工作原理相似， 因而不再另行說明。 [0026] 本發明的多燈管驅動系統10、20動態取得最高管電流與 最低管電流並進行比較，以確定是否發生異常，因而， 當環境溫度及燈管LI、L2參數變化時，最高管電流與最 低管電流均隨之變化，不會影響異常狀況的判斷，避免 誤動作的產生。 [0027] 综上所述，本發明符合發明專利要件，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例，舉凡 熟悉本案技藝之人士，在爰依本案發明精神所作之等效 修飾或變化，皆應包含於以下之申請專利範圍内。 【圖式簡單說明】 [0028] 圖1為本發明一實施方式中多燈管驅動系統的示意圖； [0029] 圖2為本發明一實施方式中多燈管驅動系統的具體電路圖 ;及 [0030] 圖3為本發明另一實施方式中多燈管驅動系統的具體電路 100103053 表單編號A0101 第12頁/共20頁 1002005413-0 201233249 [0031] 圖。 【主要元件符號說明】 多燈管驅動系統：1 0、2 0 [0032] 濾波電路：100 [0033] 脈衝寬度調變控制器：110 [0034] 開關電路：120 [0035] 異常偵測電路：130 Ο [0036] 訊號轉換電路：1300 [0037] 訊號轉換單元：1301 [0038] 最高管電流取得電路：1310 [0039] 最低管電流取得電路：1320 [0040] 比較電路：1330、1330A [0041] 比較器：1331 〇 [0042] 保護電路：140 [0043] 變壓器：ΤΙ、T2 [0044] 燈管：LI、L2 [0045] 開關：Q [0046] 第一至第五電阻：R1、R2、R3、R4、R5 [0047] 第一至第二電容：Cl、C2 [0048] 第一至第三二極體：Dl、D2、D3 100103053 表單編號A0101 第13頁/共20頁 1002005413-0 201233249 [0049] 第一參考電壓：Vccl [0050] 第二參考電壓：Vcc2 [0051] 輸入電源：Vi η 1002005413-0 100103053 表單編號Α0101 第14頁/共20頁201233249 VI. Description of the Invention: [Technical Field] [0001] The present invention relates to a backlight driving system, and more particularly to a multi-lamp driving system. [Prior Art] [0002] Cold cathode fluorescent lamps are often used as backlights for liquid crystal display screens. In order to drive the cold cathode fluorescent lamp, the inverter needs to convert the DC power to AC power to provide a suitable driving power. In order to protect the cold cathode fluorescent lamp and the inverter itself, an abnormality detection and protection circuit is often provided in the inverter to detect abnormalities and take protective measures. Usually, the anomaly detection and protection circuit compares the detected signal with the set reference voltage to determine whether to protect. However, since the set reference voltage is a fixed voltage, it is easy to cause malfunction due to changes in ambient temperature and lamp parameters. SUMMARY OF THE INVENTION [0003] In view of the above, it is desirable to provide a multi-lamp driving system that accurately detects abnormalities and avoids malfunctions. [0004] A multi-lamp driving system for driving a plurality of lamps, including a filter circuit, a switch circuit, a pulse width modulation controller, a protection circuit, a plurality of transformers, and an abnormality detecting circuit. Each of the transformers includes a primary winding and a secondary winding. The primary windings of the transformers are connected in parallel to the switching circuit, and the high voltage terminals of the secondary windings of the transformers are connected to the lamps one by one. The abnormality detecting circuit is connected to the transformer and the protection circuit for detecting whether the multi-lamp driving system and the lamps are abnormal, including a signal conversion circuit, a maximum tube current obtaining circuit, a minimum tube current obtaining circuit and a comparison circuit. The signal conversion circuit is connected to the low voltage of the secondary winding of the transformer. 100103053 Form No. A0101 Page 4 of 20 1002005413-0 201233249 压 The pressure terminal is used to convert the current signal flowing through the lamps into a voltage signal. The highest tube current acquisition circuit is connected to the signal conversion circuit for obtaining the highest voltage signal after the lamp having the highest current in the lamps. The lowest tube current acquisition circuit is connected to the signal conversion circuit for obtaining the lowest voltage signal after the lamp having the lowest current in the lamps. The comparison circuit is connected to the highest tube current acquisition circuit and the minimum tube current acquisition circuit for comparing whether the difference between the highest voltage signal and the lowest voltage signal exceeds a preset range, and at the highest voltage signal and the lowest voltage signal When the difference exceeds the preset range, a trigger signal is generated. The protection circuit controls the pulse width modulation controller to stop outputting the pulse width modulation signal when the trigger signal is received, thereby turning off the output of the switch circuit. [0006] Preferably, the signal conversion circuit includes a complex signal conversion unit, corresponding to a low voltage end of the secondary winding connecting the transformers, each of the signal conversion units includes a first resistor and a first capacitor, One end of the first resistor is connected to the low voltage end of the secondary winding of the corresponding transformer, and the other end is grounded, and the first capacitor is connected in parallel with the first resistor. Preferably, the highest tube current obtaining circuit comprises a plurality of first diodes corresponding to a low voltage end of the secondary winding connecting the signal conversion unit and the transformers, and the anodes are respectively connected to the low voltage ends of the secondary windings of the corresponding transformers The cathode is connected and outputs the highest voltage signal. [0007] Preferably, the minimum tube current acquisition circuit includes a plurality of second diodes corresponding to a low voltage end of the secondary winding connecting the signal conversion unit and the transformers, and the cathodes are respectively connected to the secondary windings of the corresponding transformers. The low voltage end, the anode is connected and receives the first reference voltage via the second resistor and inputs 100103053 Form No. 1010101 Page 5 / Total 20 pages 1002005413-0 201233249 The lowest voltage signal is output. Preferably, the comparison circuit includes a switch, a third diode, a second capacitor, and a fourth resistor. The switch includes a control electrode, a first electrode and a second electrode. The control electrode is connected to the anodes of the second diodes and grounded via a third resistor, and the first electrode is connected to the cathodes of the first diodes. The anode of the third diode is connected to the second electrode of the switch, and the cathode outputs the trigger signal. One end of the second capacitor is connected to the cathode of the third diode, and the other end is grounded. The fourth resistor is in parallel with the second capacitor. [0009] Preferably, the switch is a P-type metal oxide semiconductor field effect transistor, the control is a gate, the first electrode is a source, and the second electrode is a drain. [0010] Preferably, the comparison circuit includes a comparator, a third diode, a second capacitor, a fourth resistor, and a fifth resistor. The comparator includes a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal is coupled to the cathodes of the first diodes, and the negative input terminal is coupled to the anodes of the second diodes. The anode of the third diode is connected to the output of the comparator, and the cathode outputs the trigger signal. One end of the second capacitor is connected to the cathode of the third diode, and the other end is grounded. The fourth resistor is in parallel with the second capacitor. One end of the fifth resistor is connected to the output of the comparator, and the other end is connected to the second reference voltage. [0011] The multi-lamp driving system dynamically obtains the highest tube current and the minimum tube current and compares them to determine whether an abnormality occurs. Therefore, when the ambient temperature and the lamp parameters change, the highest tube current and the minimum tube current follow. Changes will not affect the judgment of abnormal conditions and avoid the occurrence of malfunctions. Embodiments [0012] FIG. 1 is a schematic diagram of a multi-lamp driving system 10 according to an embodiment of the present invention. 100103053 Form No. A0101 Page 6 of 20 1002005413-0 201233249 Ο In the present embodiment, the multi-lamp driving system 10 is used to convert the input power source Vin into an AC power source, and drive the plurality of lamps LI, L2 (only two For example). The input power source Vin is a DC power source. In other embodiments of the invention, the input power source V i η may also be an alternating current source. The multi-lamp driving system 10 includes a filter circuit 100, a switch circuit 120, a pulse width modulation controller 110, a complex transformer ΤΙ, Τ2, an abnormality detecting circuit 130, and a protection circuit 140. The filter circuit 100 is used for filtering. In the present embodiment, the filter circuit 10 includes a capacitor, for example, three capacitors connected in parallel with each other. The filter circuit 100 filters and outputs a DC power signal. The switch circuit 120 is connected to the filter circuit 100 for converting the DC power signal outputted by the filter circuit 100 into a first AC power signal. In this embodiment, the first alternating current power signal is a square wave signal. The switch circuit 120 includes a full bridge circuit, a half bridge circuit, a push-pull circuit, and the like. [0013] The pulse width modulation controller 110 is configured to generate a pulse width modulation signal, and the control switch circuit 120 is turned on or off to convert the DC power signal outputted by the filter circuit 100 into a first AC power signal. The protection circuit 140 is configured to protect the multi-lamp driving system 10 or the lamps LI, L2 when abnormal, and notify the pulse width modulation controller 110 to stop the pulse width modulation controller 110 from outputting the pulse width modulation signal. Switching circuit 120 stops switching, thereby turning off multi-lamp drive system 10 to avoid damage. [0014] Each transformer ΤΙ, Τ 2 includes a primary winding and a secondary winding. The primary windings of the transformers Τ and Τ2 are connected in parallel to the switching circuit 120, and the high voltage end of the secondary windings - corresponding to the connecting lamps LI, L2, that is, the high voltage end of the secondary winding of the transformer Τ1 corresponds to the connecting lamp L1, the secondary of the transformer Τ2 The high voltage end of the winding is connected to the lamp tube L2. The transformers Τ and Τ2 are used to convert the first AC power signal outputted by the switch circuit 120 100103053 Form No. Α0101 Page 7 of 20 1002005413-0 201233249 into a second AC power signal. In this embodiment, the second AC power signal is a sine wave signal. [0015] The abnormality detecting circuit 130 is connected to the transformer ΤΙ, T2 and the protection circuit 140 for detecting whether the multi-lamp driving system 10 and the lamps LI, L2 are abnormal, including the signal conversion circuit 1 300 and the highest tube current obtaining circuit 1310. The lowest tube current acquisition circuit 1 320 and the comparison circuit 1 330. The signal conversion circuit 1300 is connected to the low voltage end of the secondary winding of the transformer ΤΙ, T2 for converting the power signal flowing through the lamps LI, L2 into a voltage signal. The highest tube current acquisition circuit 1310 is connected to the signal conversion circuit 1300 for obtaining the highest voltage signal after the lamp having the highest current in the lamps L1 and L2. The minimum tube current acquisition circuit 1 320 is connected to the signal conversion circuit 1 300 for obtaining the lowest voltage signal after the lamp having the lowest current in the lamps L1 and L2 is converted. The comparison circuit 1 330 is connected to the highest tube current acquisition circuit 1310 and the lowest tube current acquisition circuit 1 320 for comparing whether the difference between the highest voltage signal and the lowest voltage signal exceeds a preset range, and at the highest voltage signal and the lowest voltage signal When the difference exceeds the preset range, a trigger signal is generated to trigger the protection circuit 140. 7伏。 In the present embodiment, the preset range can be set according to the actual situation and needs, for example, 0. 7V. The protection circuit 140 protects when the trigger signal is received, and controls the pulse width modulation controller 110 to stop outputting the pulse width modulation signal, thereby turning off the output of the switching circuit 120. [0016] The multi-lamp driving system 10 dynamically obtains the highest tube current and the minimum tube current and compares them to determine whether an abnormality has occurred, instead of the conventional fixed reference voltage comparison, and thus, the ambient temperature and the lamp LI, L2 parameter changes When the maximum tube current and the minimum tube current are changed, 100103053 Form No. A0101 Page 8 / Total 20 Page 1002005413-0 201233249 is generated. In addition, in the multi-lamp driving system 10 to carry out safety requirements items, such as contact current, when testing, the lamps LI, L2 are short-circuited so that the capacitance of the lamps L1, L2 do not participate in resonance, resulting in phase shift of the tube current signal The abnormality detecting circuit 130 can detect the abnormality and trigger the protection circuit 140. [0017] FIG. 2 is a circuit diagram of a multi-lamp driving system 10 according to an embodiment of the present invention. In the present embodiment, the signal conversion circuit 1300 includes a complex signal conversion unit 1301, corresponding to the low voltage end of the secondary winding connecting the transformers ΤΙ, T2, that is, the first signal conversion unit 1301 is connected to the transformer T1, and the second signal conversion Unit 1301 is connected to transformer T2. Each of the signal conversion units 1301 is configured to convert the current signals of the corresponding lamps L1, L2 into voltage signals, which include a first resistor K1 and a first capacitor C1. One end of the first resistor R1 is connected to the low voltage end of the secondary winding of the corresponding transformer ΤΙ, T2, and the other end is grounded, and the first capacitor C1 is connected in parallel with the first resistor R1. The first resistor R1 is used to convert the current signals of the corresponding lamps L1 and L2 into voltage signals, and the first capacitor C1 is used to filter the voltage signal converted by the first resistor R1 to obtain a stable voltage. In this embodiment, the converted voltage signal is an alternating current signal. The highest tube current acquisition circuit 1310 includes a plurality of first diodes D1, one to one corresponding to the low voltage terminals of the secondary windings of the connection signal conversion unit 1301 and the transformers ΤΙ, T2. The anodes of the first diodes D1 are respectively connected to the low voltage terminals of the secondary windings of the corresponding transformers ΤΙ, T2, and the cathodes are connected and output the highest voltage signal. The first diodes D1 filter and output the highest voltage signals among the converted voltage signals of the signal conversion unit 1301 to the comparison circuit 1330. [0019] The lowest tube current acquisition circuit 1 320 includes a plurality of second diodes D2, - 100103053 Form No. A0101 Page 9 / Total 20 pages 1002005413-0 201233249 Corresponding to the connection of the signal conversion unit 1301 and the transformer ΤΙ, T2 The low voltage end of the winding. The cathodes of the second diodes D2 are respectively connected to the low voltage terminals of the secondary windings of the corresponding transformers ΤΙ, Τ2, and the anodes are connected and receive the first reference voltage Vccl via the second resistor R2 and output the lowest voltage signal to the comparison circuit 1330. In the present embodiment, the *most voltage signal and the lowest voltage signal are all AC signals. [0020] The comparison circuit 1 330 includes a switch Q, a third diode D3, a third resistor R3, a second capacitor C2, and a fourth resistor R4. The switch Q includes a control electrode, a first electrode, and a second electrode. The control electrode of the switch Q is connected to the anode of the second diode D2, that is, receives the lowest voltage signal, and is grounded via the third resistor R3. The first electrode of the switch Q is connected to the cathode of the first diode D1, that is, the highest voltage signal is received, and the second electrode is connected to the anode of the third diode D3. The cathode of the third diode D3 outputs the trigger signal to the protection circuit. One end of the second capacitor C2 is connected to the cathode of the third diode D3, and the other end is grounded. The fourth resistor R4 is connected in parallel with the second capacitor C2. The third diode D3, the second capacitor C2, and the fourth resistor R4 are used to convert the highest voltage signal of the alternating current into a direct current signal, and then output to the protection circuit 140, that is, the trigger signal is a direct current signal. [0021] In the present embodiment, the switch Q is a P-type metal oxide semiconductor field effect transistor, and the gate is controlled to be a gate, the first electrode is a source, and the second electrode is a gate electrode. [0022] In the present embodiment, The parameters of the lamps LI and L2 are the same, the parameters of the transformers T1 and T2 are the same, the parameters of the signal conversion unit 1301 are the same, the parameters of the first diode D1 are the same, and the parameters of the second diode D2 are the same. Therefore, if the lamps LI, L2 and the multi-lamp driving system 10 are not abnormal, the currents flowing through the lamps L1 and L2 are not much different, and the difference value does not reach the preset range, and the ratio is 100103053. Form No. A0101 Page 10 of 20 Page 1002005413-0 201233249 Compared with circuit 1 330, no protection signal is generated, and protection circuit 140 is not protected. [0023] [0024] If any of lamp L1, L2 and multi-lamp drive system 10 is abnormal, for example, The lamp L1 is broken, and at this time, the current flowing through the lamp L1 is small. Therefore, the voltage of the voltage signal of the signal conversion unit 1301 corresponding to the lamp L1 is smaller than the voltage of the voltage signal of the signal conversion unit 1301 corresponding to the lamp L2. Moreover, since the first diode D1 has the same parameters and the cathodes are connected, the first diode corresponding to the lamp L2 is turned on, that is, the first diode D1 obtains the highest voltage signal corresponding to the highest current signal. The voltage of the first electrode of switch Q is equal to the highest voltage signal minus the conduction voltage drop of first diode D1. Ο At the same time, because the second diode D2 has the same parameters and the anodes are connected, the second diode D2 corresponding to the lamp L1 is turned on, that is, the second diode D2 obtains the lowest voltage signal corresponding to the lowest current signal. The voltage at the gate of switch Q is equal to the lowest voltage signal plus the turn-on voltage drop of second diode D2. The voltage difference between the control electrode of the switch Q and the first electrode is the lowest voltage plus the conduction voltage drop of the first diode D1 and the second diode D2 minus the highest voltage, because the lowest voltage is almost zero, and the highest voltage is at least For a few volts, the switch Q is turned on. At this time, the highest voltage signal is input to the anode of the third diode D3, and is rectified and filtered by the third diode D3, the second capacitor C2, and the fourth resistor R4, and then becomes a DC-type trigger signal and is input to the protection. Circuit 140. As such, the detection circuit 130 can detect an abnormality. 3 is a circuit diagram of a multi-lamp driving system 20 according to another embodiment of the present invention. The multi-lamp driving system 20 in the present embodiment is different from the multi-lamp driving system 10 in FIG. 2 in that the specific structure of the comparing circuit 1 330 is different from the comparing circuit 1330, and the rest is identical, so that it is no longer here. 100103053 Form number Α 0101 Page 11 / Total 20 pages 1002005413-0 201233249 Description. The comparison circuit 1 330A includes a comparator 1331, a third diode D3, a second capacitor C2, a fourth resistor R4, and a fifth resistor R5. The positive input terminal of the comparator 1 331 is connected to the cathode of the first diode D1, the negative input terminal is connected to the anode of the second diode D2, and the output terminal is connected to the anode of the third diode D3. One end of the fifth resistor R5 is connected to the output terminal of the comparator 1331, and the other end receives the second reference voltage. The connection relationship and action of the third diode D3, the second capacitor C2, and the fourth resistor R4 are the same as those in FIG. 2, and will not be described in detail herein. In the present embodiment, the comparison circuit 1 330A differs from the comparison circuit 1330 in FIG. 2 in that the comparator 1331 is used instead of the switch Q, but the operation principle is similar and will not be further described. The multi-lamp driving system 10, 20 of the present invention dynamically obtains the highest tube current and the lowest tube current and compares them to determine whether an abnormality occurs, and thus, when the ambient temperature and the lamp LI, L2 parameters change, the highest tube Both the current and the minimum tube current change, which does not affect the judgment of abnormal conditions and avoid the occurrence of malfunction. [0027] In summary, the present invention complies with the requirements of the invention patent, and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0028] FIG. 1 is a schematic diagram of a multi-lamp driving system according to an embodiment of the present invention; [0029] FIG. 2 is a specific circuit diagram of a multi-lamp driving system according to an embodiment of the present invention; and [0030] 3 is a specific circuit of a multi-lamp driving system according to another embodiment of the present invention. 100103053 Form No. A0101 Page 12/20 pages 1002005413-0 201233249 [0031] FIG. [Main component symbol description] Multi-lamp drive system: 1 0, 2 0 [0032] Filter circuit: 100 [0033] Pulse width modulation controller: 110 [0034] Switch circuit: 120 [0035] Anomaly detection circuit: 130 Ο [0036] Signal Conversion Circuit: 1300 [0037] Signal Conversion Unit: 1301 [0038] Maximum Tube Current Acquisition Circuit: 1310 [0039] Minimum Tube Current Acquisition Circuit: 1320 [0040] Comparison Circuit: 1330, 1330A [0041] Comparator: 1331 〇 [0042] Protection circuit: 140 [0043] Transformer: ΤΙ, T2 [0044] Lamp: LI, L2 [0045] Switch: Q [0046] First to fifth resistors: R1, R2, R3 , R4, R5 [0047] First to second capacitors: Cl, C2 [0048] First to third diodes: Dl, D2, D3 100103053 Form No. A0101 Page 13 / Total 20 pages 1002005413-0 201233249 [ 0049] First reference voltage: Vccl [0050] Second reference voltage: Vcc2 [0051] Input power: Vi η 1002005413-0 100103053 Form number Α 0101 Page 14 of 20