1355864 99年3月24曰申復補充修正修正版 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種發光裝置及其軀動方法，特別關於 一種具有發光二極體之發光裝置與發光裝置之驅動方法。 【先前技術】. 發光二極體一般係利用P型半導體以及N型半導體製 作而成，由於利用半導體元件所製作的發光二極體，具有 壽命長、點燈速度快、光電轉換效率高、體積小以及光譜 窄等優點，近來受到相當的重視，也因此加速了發光二極 體技術的成長。 圖.1為顯示習知之發光裝置之一示意圖。如圖1所 示，一發光裝置1包含一電源供應電路11、一變壓器12、 一穩壓電容13、一諧振式濾波器14、一箝位器15、複數 個發光單元16〜18、以及一發光期間控制電路19，各發光 單元16〜18分別包含三個發光二極體161〜181以及一開關 162〜182，電源供應電路11電性連接至變壓器12以提供 一電壓VIN，變壓器12轉換電壓VIN以輸出一電壓V0UT， 穩壓電容13電性連接至變壓器12以穩定電壓VOUT，諧振 式濾波器14電性連接至變壓器12並對電壓V0UT濾波藉 以消除高頻突波，各發光單元16〜18透過濾波器Ί_4電性 連接至變壓器12，電壓V0UT係驅動各發光單元16〜18之 發光二極體161〜181發光。 發光期間控制電路19電性連接至開關162、172和 5 1355864 99年3月24日申復補充修正修正版 182，並控制開關162、172和182分別於第一期間二第二 期間和第三期間導通發光二極體161、171、181與變壓器 12 ’藉以控制電壓V〇ut於各期間分別驅動發光二極體 161 、 171 、 181 。 發光二極體161、171、181係設定為發出藍色、紅色、 綠色光線，然而，由於各發光單元161、171、181的額定 驅動電壓不一樣，例如電壓VOUT必須降低藉以從驅動發 光單元161改為驅動發光單元171，在轉態時，箝位器15 係用以消耗過多之功率，藉以避免仍有過高的殘留電壓 V〇UT驅動發光單元171而造成發光單元171之發光波長偏 移或影響其使用壽命。另外，在此架構下，諧振式濾波器 14與箝位器15.亦會造成額外的成本。 因此如何提供一種發光裝置及其驅動方法.，使其減少 殘留電壓，實屬當前重要課題之一。 【發明内容】 有鑑於上述課題，本發明之目的為提供一種具有減少 殘留電壓之發光裝置，以及減少殘留電壓之驅動方法。 緣是，為達上述目的，依本發明之一種發光裝置之驅 動方法，係先後驅動一第一發光二極體與一第二發光二極 體分別於一第一期間與一第二期間發光，該驅動方法包含 以下步驟：於第一期間内，輸出具有一第一責任週期之一 驅動訊號，以驅動第一發光二極體；以及於第一期間内， 輸出具有一第二責任週期之驅動訊號，以驅動第一發光二 1355864 99年3月24曰申復補充修正修正版 極體，其中第二責任遇期小於第一責任週期。 緣是，為達上述目的，依本發明之一種發光裝置包含 - 一電源供應電路、一變壓器、一第一發光單元、一第二發 . 光單元、以及一變壓器開關，電源供應電路輸出一電壓； 變壓器具有一一次側及一二次側，一次側係電性連接至電 源供應電路，以轉換電壓並由二次侧輸出一驅動訊號；第 一發光單元電性連接至變壓器之二次側，並由驅動訊號所 驅動而於一第一期間發光；第二發光單元電性連接至變壓 鲁 器之二次側，並由驅動訊號所驅動而於一第二期間發光， 其中第一發光單元與第二發光單元並聯；變壓器開關電性 連接至變壓器，於第一期間内，先後接收具有一第一責任 週期與一第二責任週期之一 PWM控制訊號，以控制變壓 器輸出.具有第一責任週期與第二責任週期之驅動訊號，其 中第二責任週期小於第一責任週期。 承上所述，因依本發明之發光裝置及其驅動方法中， φ 於第一期間内，驅動訊號係先後具有第一責任週期以及第 二責任週期，且第二責任週期小於第一責任週期，使得在 第一期間與第二期間轉態前，驅動訊號的平均電壓能夠適 當地降低，因而可避免在第二期間仍有過高的電壓來驅動 第二發光二極體。 【實施方式】 以下將參照相關圖式，說明依本發明較佳實施例之發. 光裝置及其驅動方法。 1355864 99年3月24日申復補充修正修正版 圖2為顯示依本發明較佳實施例之發光裝置之一示意 圖。如圖2所示，一發光裝置2包含一第一發光單元21、 一第二發光單元22、一第三發光單元23、一電源供應電 路24、一變壓器25、一變壓器開關26、一 PWM控制電 路27、一發光期間控制電路28、一二極體291、以及一電 容器292。 電源供應電路24輸出一電壓V，變壓器25具有—— 次側及一二次侧，一次側係電性連接至電源供應電路24， 以轉換電壓V並輸出一驅動訊號S，第一發光單元21、第 二發光單元22、與第三發光單元23係並聯，並電性連接 至變壓器25之二次側，且分別於一第一期間、一第二期 間、一第三期間由驅動訊號S所驅動而發光。變壓器開關 + 26電性連接至變壓器25，其係受控於一 PWM控制訊號 CNT。 圖3為顯示依本發明較佳實施例之發光裝置中PWM 控制訊號與驅動訊號之一波形圖。如圖3所示，於第一期 間内，PWM控制訊號CNT先後具有一第一責任週期與一 第二責任週期，第二責任週期係小於第一責任週期，變壓 器開關26係控制電源供應電路24是否輸出電壓V至變壓 器25,並藉以控制變壓器25所輸出之驅動訊號S與PWM 控制訊號CNT對應，驅動訊號S亦同樣具有第一責任週 期與第二責任週期。 請再參照圖2，在本實施例中，電容器292係與第一 發光單元21、第二發光單元22與第三發光單元23並聯， 1355864 99年3月24日申復補充修正修正版 其係用於穩定驅動訊號S之電壓，第一發光單元21、第二 發光單元22與第三發光單元23係透過二極體291電性連 ^ 接至變壓器25，二極體291係防止逆電流驅動這些發光單 .元。 第一發光單元21包含一第一發光二極體211以及一 開關212，第一發光二極體211電性連接至變壓器25，開 關212電性連接至第一發光二極體211 ;第二發光單元22 包含一第二發光二極體221以及一開關222，第二發光二 • 極體221電性連接至變壓器25，開關222電性連接至第二 發光二極體221 ;第三發光單元23包含一第三發光二極體 • 231以及一開關232，第三發光二極體231電性連接至變 壓器25，開關232電性連接至第三發光二極體231。 •發光期間控制電路28電性連接至開關212、222和 232，並控制開關212、222和232分別於第一期間、第二 期間和第三期間導通，藉以控制驅動訊號S於各期間分別 φ 驅動第一發光二極體211、第二發光二極體221、和第三 發光二極體231。 第一發光二極體211、第二發光二極體221、以及第 三發光二極體231分別為藍光二極體、紅光二極體、以及 綠光二極體，第一發光二極體211之額定驅動電壓高於第 二發光二極體221之額定驅動電壓，第二發光二極體221 之額定驅動電壓高於第三發光二極體231之額定驅動電 壓。 請再參照圖3，於本實施例中，係以於第一期間驅動 9 1355864 99年3月24日申復補充修正修正版 藍色發光二極體，於第二期間驅動紅色發光二極體，於第 三期間驅動綠色發光二極體為例，為了能夠順利驅動各不 同額定驅動電壓的發光二極體，電源供應電路24在第一 期間、第二期間和第三期間時，其所提供的電壓V之值分 別為Vi、V2和V3，其中V:大於V2，V2大於V3，因此， 變壓器25於各期間轉換各對應電壓V，使得驅動訊號S 在第一期間時之平均電壓值V!高於在第二期間時之平均 電壓值V2，並且在第二期間時之平均電壓值V2高於在第 三期間時之平均電壓值V3。 另外，若於第一期間驅動綠色發光二極體，於第二期 間驅動藍色發光二極體，於第三期間驅動紅色發光二極 體，則驅動訊號S在第一期間時之平均電壓值V}.低於在 第二期間時之平均電壓值V2。 另外，在第一期間内，驅動訊號S先後分別具有第一 責任週期與第二責任週期，其中第二責任週期小於第一責 任週期，驅動訊號S具有第一責任週期時之平均電壓值 Vu高於具有第二責任週期時之平均電壓值V12，且平均電 壓值V12介於第一發光二極體211之額定驅動電壓與第二 發光二極體221之額定驅動電壓之間，如此一來，在第一 期間與第二期間轉態前，驅動訊號S的平均電壓將適當地 降低，因而可避免在第二期間仍有過高的電壓來驅動第二 發光二極體22。 另外，變壓器開關26於第一期間内，接收具有一第 三貴任週期之PWM控制訊號CNT，藉以控制變壓器25 輸出具有第三責任週 鱗④則讎修正麵1355864 March 24, 1999, Shen Fu, Supplementary Amendment, IX. Description of the Invention: [Technical Field] The present invention relates to a light-emitting device and a method for the same, and more particularly to a light-emitting device having a light-emitting diode A method of driving a light-emitting device. [Prior Art] A light-emitting diode is generally fabricated using a P-type semiconductor and an N-type semiconductor, and has a long life, a fast lighting speed, a high photoelectric conversion efficiency, and a volume due to a light-emitting diode fabricated using a semiconductor element. The advantages of small size and narrow spectrum have recently received considerable attention, which has accelerated the growth of light-emitting diode technology. Fig. 1 is a schematic view showing a conventional illuminating device. As shown in FIG. 1 , a light-emitting device 1 includes a power supply circuit 11 , a transformer 12 , a voltage stabilizing capacitor 13 , a resonant filter 14 , a clamp 15 , a plurality of light-emitting units 16 to 18 , and a In the light-emitting period control circuit 19, each of the light-emitting units 16 to 18 includes three light-emitting diodes 161 to 181 and a switch 162 to 182, and the power supply circuit 11 is electrically connected to the transformer 12 to provide a voltage VIN, and the transformer 12 converts the voltage. VIN outputs a voltage VOUT, the voltage stabilizing capacitor 13 is electrically connected to the transformer 12 to stabilize the voltage VOUT, and the resonant filter 14 is electrically connected to the transformer 12 and filters the voltage V0UT to eliminate high frequency spurs, and each of the light emitting units 16~ The transmission filter Ί_4 is electrically connected to the transformer 12, and the voltage VOUT drives the light-emitting diodes 161 to 181 of the respective light-emitting units 16 to 18 to emit light. The illumination period control circuit 19 is electrically connected to the switches 162, 172, and 5 1355864. On March 24, 1999, the supplementary correction correction version 182 is applied, and the switches 162, 172, and 182 are controlled in the second period and the third period, respectively. During the period, the light-emitting diodes 161, 171, and 181 and the transformer 12' drive the light-emitting diodes 161, 171, and 181, respectively, by the control voltage V〇ut. The light-emitting diodes 161, 171, and 181 are set to emit blue, red, and green light. However, since the rated driving voltages of the respective light-emitting units 161, 171, and 181 are different, for example, the voltage VOUT must be lowered to drive the light-emitting unit 161. Instead, the light-emitting unit 171 is driven. In the transition state, the clamp 15 is used to consume excessive power, so as to avoid the excessive residual voltage V〇UT driving the light-emitting unit 171 to cause the light-emitting wavelength of the light-emitting unit 171 to shift. Or affect its service life. In addition, under this architecture, the resonant filter 14 and the clamp 15. also incur additional costs. Therefore, how to provide a light-emitting device and a driving method thereof to reduce the residual voltage is one of the current important topics. SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a light-emitting device having a reduced residual voltage and a driving method for reducing a residual voltage. In order to achieve the above object, in accordance with a driving method of a light-emitting device of the present invention, a first light-emitting diode and a second light-emitting diode are sequentially driven to emit light in a first period and a second period, respectively. The driving method includes the steps of: outputting a driving signal having a first duty cycle to drive the first light emitting diode during the first period; and outputting the driving with a second duty cycle in the first period The signal to drive the first illuminating two 1355864 March 24, 2014 曰 补充 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补 补In order to achieve the above object, a light-emitting device according to the present invention comprises: a power supply circuit, a transformer, a first light-emitting unit, a second light-emitting unit, and a transformer switch, and the power supply circuit outputs a voltage The transformer has a primary side and a secondary side, the primary side is electrically connected to the power supply circuit to convert the voltage and output a driving signal from the secondary side; the first lighting unit is electrically connected to the secondary side of the transformer And driving by the driving signal to emit light in a first period; the second lighting unit is electrically connected to the secondary side of the transformer, and is driven by the driving signal to emit light in a second period, wherein the first light is emitted The unit is connected in parallel with the second lighting unit; the transformer switch is electrically connected to the transformer, and receives a PWM control signal having a first duty cycle and a second duty cycle to control the transformer output during the first period. The driving cycle of the responsibility cycle and the second duty cycle, wherein the second duty cycle is less than the first duty cycle. As described above, in the illuminating device and the driving method thereof according to the present invention, φ is in the first period, the driving signal system has the first duty cycle and the second duty cycle, and the second duty cycle is less than the first duty cycle. Therefore, before the first period and the second period transition state, the average voltage of the driving signal can be appropriately lowered, so that it is possible to avoid excessive voltage during the second period to drive the second light emitting diode. [Embodiment] Hereinafter, an optical device and a driving method thereof according to a preferred embodiment of the present invention will be described with reference to the related drawings. 1355864 March 24, 1999 Application Supplementary Correction Revision FIG. 2 is a schematic view showing a light-emitting device according to a preferred embodiment of the present invention. As shown in FIG. 2, a light-emitting device 2 includes a first light-emitting unit 21, a second light-emitting unit 22, a third light-emitting unit 23, a power supply circuit 24, a transformer 25, a transformer switch 26, and a PWM control. The circuit 27, a light-emitting period control circuit 28, a diode 291, and a capacitor 292. The power supply circuit 24 outputs a voltage V. The transformer 25 has a secondary side and a secondary side. The primary side is electrically connected to the power supply circuit 24 to convert the voltage V and output a driving signal S. The first lighting unit 21 The second light-emitting unit 22 is connected in parallel with the third light-emitting unit 23 and electrically connected to the secondary side of the transformer 25, and is driven by the driving signal S in a first period, a second period, and a third period, respectively. Drive and shine. The transformer switch + 26 is electrically connected to the transformer 25, which is controlled by a PWM control signal CNT. 3 is a waveform diagram showing PWM control signals and driving signals in a lighting device according to a preferred embodiment of the present invention. As shown in FIG. 3, during the first period, the PWM control signal CNT has a first duty cycle and a second duty cycle, the second duty cycle is less than the first duty cycle, and the transformer switch 26 controls the power supply circuit 24 Whether the voltage V is output to the transformer 25, and the driving signal S outputted by the control transformer 25 corresponds to the PWM control signal CNT, and the driving signal S also has a first duty cycle and a second duty cycle. Referring to FIG. 2 again, in the embodiment, the capacitor 292 is connected in parallel with the first light-emitting unit 21, the second light-emitting unit 22, and the third light-emitting unit 23, and 1355864 is applied for a supplemental revision revision on March 24, 1999. The first light-emitting unit 21, the second light-emitting unit 22, and the third light-emitting unit 23 are electrically connected to the transformer 25 through the diode 291, and the diode 291 prevents reverse current driving. These luminous singles. Yuan. The first illuminating unit 21 includes a first illuminating diode 211 and a switch 212. The first illuminating diode 211 is electrically connected to the transformer 25. The switch 212 is electrically connected to the first illuminating diode 211. The unit 22 includes a second LED 221 and a switch 222. The second LED 221 is electrically connected to the transformer 25. The switch 222 is electrically connected to the second LED 221. The third LED 23 is The third light emitting diode 231 is electrically connected to the transformer 25, and the switch 232 is electrically connected to the third light emitting diode 231. The illumination period control circuit 28 is electrically connected to the switches 212, 222, and 232, and controls the switches 212, 222, and 232 to be turned on during the first period, the second period, and the third period, respectively, thereby controlling the driving signal S in each period φ. The first light emitting diode 211, the second light emitting diode 221, and the third light emitting diode 231 are driven. The first light-emitting diode 211, the second light-emitting diode 221, and the third light-emitting diode 231 are respectively a blue LED, a red diode, and a green diode, and the first LED 211 The rated driving voltage is higher than the rated driving voltage of the second LED 221, and the rated driving voltage of the second LED 221 is higher than the rated driving voltage of the third LED 231. Referring to FIG. 3 again, in the embodiment, the first-period driving 9 1355864 is applied to the supplementary correction correction blue light-emitting diode on March 24, 1999, and the red light-emitting diode is driven in the second period. For example, driving the green light-emitting diode in the third period, in order to smoothly drive the light-emitting diodes of different rated driving voltages, the power supply circuit 24 is provided during the first period, the second period, and the third period. The values of the voltage V are Vi, V2 and V3, respectively, wherein V: is greater than V2, and V2 is greater than V3. Therefore, the transformer 25 converts each corresponding voltage V during each period so that the average voltage value V of the driving signal S during the first period is ! is higher than the average voltage value V2 at the second period, and the average voltage value V2 at the second period is higher than the average voltage value V3 at the third period. In addition, if the green light-emitting diode is driven in the first period, the blue light-emitting diode is driven in the second period, and the red light-emitting diode is driven in the third period, the average voltage value of the driving signal S in the first period is V}. is lower than the average voltage value V2 during the second period. In addition, during the first period, the driving signal S has a first duty cycle and a second duty cycle, wherein the second duty cycle is less than the first duty cycle, and the average voltage value Vu of the driving signal S has the first duty cycle. The average voltage value V12 is between the rated driving voltage of the first LED 211 and the rated driving voltage of the second LED 221, so that Before the first period and the second period transition state, the average voltage of the driving signal S will be appropriately lowered, so that excessive voltage is still prevented from driving the second light emitting diode 22 during the second period. In addition, the transformer switch 26 receives the PWM control signal CNT having a third duty cycle during the first period, thereby controlling the output of the transformer 25 to have the third duty cycle 4
於第-期間内先後 ：訊說s。爾控制訊號CNT 第二責任週期，其；第三：責任週期、第-責任週期、和 動訊號S且有當貝彳壬週期小於第一責任週期。驅 電壓值v13低於具有第 —責任週期時之平均電壓值Vu。 此外，如圖4所示，於宽 導通，使得艇動訊號8之電内，開關212係逐漸 漸關閉，使得驅動訊號8:=漸增加。開關212係逐 立沾θ 甘主 <電壓值逐漸減少。於此特別注 二^則、貝任週期係從第三責任週期由小逐漸變大為第 二再從第-責任週期由大逐漸變小為第二責任 週期° ”中’於開關元件212逐漸導通或關閉的驅動方式 中’只要開關元件212所採用的功率半導體開關減緩其導 通的速度’使功率半導體開關在進人完全導通前可經過線 I1 生放大區的操作階段’即可實現開關元件川逐漸導通的 驅動；同樣地，在開關元件212逐漸關閉的驅動方式中， 也是使功率半導體開關在進人完全截止前經過線性放大 區的操作階段，即可實現開關元件2! 2逐漸關閉的驅動。 因此’本發_開關元件212只需採用可以增加驅動的功 率半導體開關於線性放大區操作時間的電路，即可實現開 關元件212逐漸導通或逐漸關閉，進而使得驅動訊號s ^ 電壓值逐漸增加或減少。 圖5為顯示依本發明較佳實施例之發光裝置中 控制訊號與驅動訊號之另一波形圖。如圖5所示，變壓器 1355864 99年3月24日申復補充修正修正版 開關26於第二期間，接收具有一第四責任週期之PWM控 制訊號CNT，以控制變壓器25輸出具有第四責任週期之 驅動訊號S。 請再參照圖5，再者，於第二期間，變壓器開關26更 接收具有一第五責任週期之PWM控制訊號CNT，以控制 變壓器25輸出具有第五責任週期之驅動訊號S，其中第五 責任週期小於第四責任週期，因而在第二期間内，驅動訊 號S先後分別具有第四責任週期與第五責任週期，驅動訊 號S具有第四責任週期時之平均電壓值V21高於具有第五 貴任週期時之平均電壓值V22，且平均電壓值V22介於第 二發光二極體22之額定驅動電壓與第三發光二極體23之 額定驅動電壓之間，如此一來，在第二期間與第三期間轉 態前，驅動訊號S的平均電壓將適當地降低'，因而可避免 在第三期間仍有過高的電壓來驅動第三發光二極體23。 圖6為顯示依本發明較佳實施例之發光裝置2之另一 示意圖。如圖6所示，與圖2所示不同之處在於各第一發 光單元21包含複數個串聯之第一發光二極體211，第二發 光單元22包含複數個串聯之第二發光二極體221，第三發 光單元23包含複數個串聯之第二發光二極體231。且發光 裝置2包含複數個第一發光單元21、第二發光單元22、 以及第三發光單元23，這些發光單元係排列成一個發光陣 列。 综上所述，因依本發明之發光裝置及其驅動方法中， 於第一期間内，驅動訊號係先後具有第一責任週期以及第 12 1355864 99年3月24日申復補充修正修正版 二責任週期，且第二責任週期小於第一責任週期，使得在 第一期間與第二期間轉態前，驅動訊號的平均電壓能夠適 .當地降低，因而可避免在第二期間仍有過高的電壓來驅動 .第二發光二極體。 以上所述僅為舉例性，而非為限制性者。任何未脫離 本發明之精神與範疇，而對其進行之等效修改或變更，均 應包含於後附之申請專利範圍中。 •【圖式簡單說明】 圖1為顯示習知之發光裝置之一示意圖； 圖2為顯示依本發明較佳實施例之發光裝置之一示意 圖； 圖3為顯示依本發明較佳實施例之發光裝置中PWM 控制訊號與驅動訊號之一波形圖； 圖4為顯示依本發明較佳實施例之發光裝置中第一期 φ 間内驅動訊號之一波形圖； 圖5為顯示依本發明較佳實施例之發光裝置中PWM 控制訊號與驅動訊號之另一波形圖；以及 圖6為顯示依本發明較佳實施例之發光裝置之另一示 意圖。 元件符號說明： 1 發光裝置 11 :電源供應電路 12 :變壓器 13 :穩壓電容 S :驅動訊號 V、Vin、V〇ut Vll、Vl2、Vl3 :平均電壓值 V2I、V*22 :平均電壓值 1355864 14 :諧振式濾波器 16、17、18 :發光單元 162、172、182 :開關 2 :發光裝置 211第一發光二極體 22 :第二發光單元 222 :開關 231第三發光二極體 24 :電源供應電路 26 :變壓器開關 28 :發光期間控制電路 292 :電容器 99年3月24日申復補充修正修正版 15 :箝位器 161、171、181 :發光二極體 19 :發光期間控制電路 21 :第一發光單元 212 :開關 221第二發光二極體 23 :第三發光單元 232 :開關 25 :變壓器 27 : PWM控制電路 291 :二極體 CNT : PWM控制訊號 :電壓 14In the first period of time: the news said s. The second control cycle of the control signal CNT, the third; the duty cycle, the first-responsibility cycle, and the motion signal S and have a Bellow cycle less than the first duty cycle. The drive voltage value v13 is lower than the average voltage value Vu at the first duty cycle. In addition, as shown in Fig. 4, in the wide conduction, the switch 212 is gradually turned off within the power of the boat signal 8, so that the drive signal 8: = gradually increases. The switch 212 is erected θ 甘 main < voltage value is gradually reduced. In this particular note, the Bayer cycle is gradually changed from small to second from the third duty cycle, and then gradually decreased from large to second duty cycle from the first-responsibility cycle. In the driving mode of turning on or off, 'as long as the power semiconductor switch used by the switching element 212 slows down the speed of its conduction', the switching element can be realized by the operation phase of the power semiconductor switch before the full conduction of the line can be passed through the line I1. In the driving mode in which the switching element 212 is gradually turned off, in the driving mode in which the power semiconductor switch passes through the linear amplification region before the input is completely cut off, the switching element 2! 2 can be gradually turned off. Therefore, the 'initial_switching element 212 only needs to adopt a circuit that can increase the operating time of the driving power semiconductor switch in the linear amplification region, so that the switching element 212 can be gradually turned on or gradually turned off, thereby gradually increasing the driving signal s ^ voltage value. FIG. 5 is a diagram showing control signals and driving signals in a lighting device according to a preferred embodiment of the present invention. Another waveform diagram. As shown in FIG. 5, the transformer 1355864 applies for the supplemental correction correction switch 26 on March 24, 1999, and receives the PWM control signal CNT having a fourth duty cycle to control the output of the transformer 25 during the second period. The driving signal S having the fourth duty cycle. Referring again to FIG. 5, in the second period, the transformer switch 26 further receives the PWM control signal CNT having a fifth duty cycle to control the output of the transformer 25 to have the fifth responsibility. The driving signal S of the cycle, wherein the fifth duty cycle is less than the fourth duty cycle, so in the second period, the driving signal S has a fourth duty cycle and a fifth duty cycle, respectively, and the driving signal S has a fourth duty cycle. The average voltage value V21 is higher than the average voltage value V22 when the fifth noble period is present, and the average voltage value V22 is between the rated driving voltage of the second light emitting diode 22 and the rated driving voltage of the third light emitting diode 23. Therefore, before the second period and the third period transition state, the average voltage of the driving signal S will be appropriately lowered, so that it is avoided that the third period is still too high. The voltage is used to drive the third light-emitting diode 23. Fig. 6 is another schematic view showing a light-emitting device 2 according to a preferred embodiment of the present invention. As shown in Fig. 6, the difference from that shown in Fig. 2 is that each first light-emitting device The unit 21 includes a plurality of first light emitting diodes 211 connected in series, the second light emitting unit 22 includes a plurality of second light emitting diodes 221 connected in series, and the third light emitting unit 23 includes a plurality of second light emitting diodes 231 connected in series. The illuminating device 2 includes a plurality of first illuminating units 21, second illuminating units 22, and third illuminating units 23, and the illuminating units are arranged in a illuminating array. In summary, the illuminating device according to the present invention In the driving method, during the first period, the driving signal system has the first duty cycle and the second duty cycle of the supplementary amendment correction version 2 of the 12th, 1355, 1984, and the second duty cycle is less than the first responsibility cycle. Therefore, before the first period and the second period transition state, the average voltage of the driving signal can be appropriately reduced, thereby avoiding excessive voltage during the second period to drive the second light emitting diode. The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the present invention are intended to be included in the scope of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a conventional light-emitting device; FIG. 2 is a schematic view showing a light-emitting device according to a preferred embodiment of the present invention; FIG. 3 is a view showing a light-emitting device according to a preferred embodiment of the present invention. FIG. 4 is a waveform diagram showing driving signals in the first period of φ in the illuminating device according to the preferred embodiment of the present invention; FIG. 5 is a view showing a preferred embodiment of the present invention. Another waveform diagram of the PWM control signal and the driving signal in the illuminating device of the embodiment; and FIG. 6 is another schematic view showing the illuminating device according to the preferred embodiment of the present invention. Symbol description: 1 Light-emitting device 11: Power supply circuit 12: Transformer 13: Voltage-stabilizing capacitor S: Drive signal V, Vin, V〇ut Vll, Vl2, Vl3: Average voltage value V2I, V*22: Average voltage value 1355864 14 : Resonant filter 16, 17, 18: light-emitting unit 162, 172, 182: switch 2: light-emitting device 211 first light-emitting diode 22: second light-emitting unit 222: switch 231 third light-emitting diode 24: Power supply circuit 26: Transformer switch 28: Illumination period control circuit 292: Capacitor March 24, 1999 Application supplementary correction correction 15: Clamps 161, 171, 181: Light-emitting diode 19: Illumination period control circuit 21 : first light emitting unit 212 : switch 221 second light emitting diode 23 : third light emitting unit 232 : switch 25 : transformer 27 : PWM control circuit 291 : diode CNT : PWM control signal : voltage 14