200950587 i 九、發明說明： 【發明所屬之技術領域】 本發明係有關於發光二極體，特別有關於驅動複數發 光二極體之電路。 【先前技術】 近年來，發光二極體（LED)之製造及應用技術已有長 足的進步，LED以其耐用性及省電性之優點，已逐漸取代 ❹ 傳統先源，諸如日光燈（fluorescent lamp)、白熾燈泡 (incandescent lamp)、鹵素燈泡(halogen bulb)、交通號言志燈 (traffic light)乃至於液晶面板（LCD panel)之背光源等等不一 而足。LED燈具近來多朝向組成LED陣列之方式發展，以 提高其亮度。 LED係為一種具有PN接面之半導體元件，在順向電 流（forward current)通過時，可發出光線，LED具有一重要特 ^ 性，即其發光強度（luminous intensity)與順向電流係成正比關 係，即順向電流愈大，則發光強度愈高，但較大的順向電 流亦會伴隨產生較高的熱量，熱量過高極可能對LED造成 永久性的損害或壽命的大幅縮短，因此LED製造廠商皆會 對其所製造的每一型LED定出一適用於連續使用之平均順 向電壓（average forward current，Iavg)，以及另一適用於瞬間使 用之峰值順向電流（peak pulse forward current, Ipeak)，後者必高 於前者，當LED以高頻點滅時，可施加較高之峰值順向電 流以產生較高之瞬時發光強度（instantaneous luminous 5 200950587 f intensity)，·而當LED係連續點亮時，則僅能施加較低之平 均順向電流，其所產生之發光強度為連續且一致的，但必 低於前述以峰值順向電流所產生之瞬時發光強度。 習知的LED燈具皆採連續點亮之操作模式，故僅能施 加較j之平均順向電流，若需提高發光強度時，僅能以更 換更咼功率的LED來加以解決，但毫無疑問的，此舉必會 耗費相當的購置成本，且其散熱問題亦勢必更難比解決， ❹另一方面，LED產品之發展並非一蹴可幾，每一時期均有 f發展上的限制，不可能有完全符合使用需求之產品在市 場上，例如目前low以上的單顆LED即已不易在市場上見 到，故若能將現有LED產品提高其發光強度又不致造成發 熱量增加及壽命縮短等問題，必有其需求存在。 【發明内容】 人眼具有視覺暫留之特性，對於高頻閃爍之發光體會 ❹產生連續發光之錯覺，例如-般螢光燈管（曰光燈）若以 變壓器式安定器驅動，則必會產生交流市電頻率兩倍的閃 爍頻率（因在一個弦波週期中有兩個零交越點），即6〇1^ 市電將產生120Hz之閃爍頻率，此種閃爍頻率人眼仍可察 覺’、甚至對人眼有不利之影響，故有較高階之燈具改採電 子式安定器，將電源頻率轉換至約1〇〜3〇kHz的高頻 ^閃爍頻率升高至2〇〜嶋z，此一高頻閃燦已超出人眼所 犯察覺的範圍，而產生一種連續發光之視覺效果，易言 之，對LED而言，其係閃爍點滅發光，但對人眼而言，其 6 200950587 f 為連續發光。 本發明即利用此一特性，對複數LED或LED陣列施加 高頻切換之不連續電流，並使其循序點滅，且該電流可高 於平均順向電流’甚至可達峰值順向電流之上限，藉此以 提高LED之發光強度，且不致增加LED之發熱量，可節省 使用更高功率LED所需之購置成本，並可避免隨之而生的 散熱問題。 ❿【實施方式】 首請參閱第一圖’其係為本發明之電路方塊圖，主要 係由一脈寬調變（PWM)產生器⑴、複數個調光式定電流源 (dimming constant current source) (2a〜2f)及複數個 LED 陣列 (3 a〜3 f)，其中調光式定電流源（2a〜2f)與LED陣列（3 a〜3 f)係 為相同數量’並為一對一配置，圖中所示者係以六組為 例，當然亦可為其他除1以外的任何數量，另一方面，此 ❹處說明係以六個LED陣列（3a〜3f)組成一個更大的陣列，舉 例而言，若每一 LED陣列（3a〜3f)係由1〇顆LED所組成，則 六個LED陣列（3a〜3f)將組成一個具有60顆LED的更大陣 列，當然該單一 LK)陣列（3a〜3f)亦可為單一 LED，而以六 個LED組成一個LED陣列。另所謂的調光式定電流源 (2a〜2f)，係指一種具有PWM訊號輸入端之直流定電流源， 其定電流輸出可受PWM訊號之控制而產生同步中斷，如聚 積公司（MACR0BL0CK)所生產之MBI6650型號之直流轉直 流轉換器（DC/DC converter)積體電路，其第二腳之調光控制 7 200950587 端（pimming control terminal, DIM)即可做為 PWM訊號輸入端。 該調光式定電流源（2a〜2f)之PWM訊號輸入端係分別連 接至PWM產生器⑴之PWM訊號輸出端，該PWM產生器⑴可 輸出與其相同數量之PWM訊號，並分別輸出，該PWM訊號 之時序繪示於第二圖中，每一組PWM訊號均為週期性，且 其週期（T)及工作週期⑷皆相同，亦即每一PWM訊號之脈 衝期間（r)皆相同，假設所驅動的LED陣列（3a〜3f)數量為 η，則工作週期d係為η的倒數，即d=l/n，且其脈衝部份 ® 係在時間上依序接續，亦即一第一PWM訊號中之脈衝係為 一第二PWM訊號之脈衝所緊密跟隨，第一PWM訊號之脈衝 結束之同時，第二PWM訊號之脈衝即發生，如此依序類 推，假設脈衝期間7： =lms，且n=6，則每一 PWM訊號之週 期T即等於6ms，工作週期d=l/6与16.67%。 每一 PWM訊號係輸出至一對應之調光式定電流源 (2a〜2f)，使該調光式定電流源（2a〜2f)分別輸出與所輸入 @ PWM訊號相同時序之定電流驅動電力至每一 LED陣列 (3a〜3f)，使該LED陣列（3a〜3f)產生與第二圖相同之高頻循 序點滅，亦即每一個單一 LED陣列（3a〜3f)之點滅頻率為 1/THz，全部LED[陣列（3a〜3f)之整體點滅頻率為η/ΤΗζ， 承前述所例示之數字，則每一個單一 LED陣列（3a〜3f)之點 滅頻率為166.7Hz，整體點滅頻率為1kHz，若將每一 PWM訊 號之脈衝期間r設為0.1ms ，整體點滅頻率即上升為 10kHz ;若r=0.05ms，則整體點滅頻率將上升至20kHz ； 若τ: =0.0286ms，則整體點滅頻率將上升至35kHz。 8 200950587 本發明將複數LEDP車列（3a〜3f)以高頻循環點 加高於LED額定平均順向電流之驅動電流，使其瞬並施 強度增加，再藉由人眼之視覺暫留特性，使得”2 = 發光強度形成相當於連續發光強度之視覺效果，， 整體亮度提升之功效。 卩違成200950587 i IX. Description of the Invention: [Technical Field of the Invention] The present invention relates to a light-emitting diode, and more particularly to a circuit for driving a plurality of light-emitting diodes. [Prior Art] In recent years, the manufacturing and application technology of light-emitting diodes (LEDs) has made great progress. LEDs have gradually replaced traditional sources such as fluorescent lamps with their durability and power saving advantages. ), incandescent bulbs, halogen bulbs, traffic lights, and backlights for LCD panels, to name a few. Recently, LED lamps have been developed in such a way as to form LED arrays to increase their brightness. LED is a semiconductor component with a PN junction. When a forward current passes, it emits light. The LED has an important characteristic, that is, its luminous intensity is proportional to the forward current system. The relationship, that is, the higher the forward current, the higher the luminous intensity, but the larger forward current is also accompanied by the generation of higher heat, which may cause permanent damage to the LED or greatly shorten the life. LED manufacturers will specify an average forward current (Iavg) for each type of LED they manufacture, and another peak forward current for transient use. Current, Ipeak), after the latter is higher than the former, when the LED is extinguished at a high frequency, a higher peak forward current can be applied to generate a higher instantaneous luminous intensity (instantaneous luminous 5 200950587 f intensity), and when the LED When continuously lighting, only a lower average forward current can be applied, and the luminous intensity produced is continuous and consistent, but must be lower than the aforementioned peak forward current. The instantaneous light emission intensity is generated. The conventional LED lamps adopt continuous operation mode, so only the average forward current of j can be applied. If the luminous intensity needs to be increased, only the LED with more power can be replaced, but there is no doubt. The move will inevitably cost a considerable amount of acquisition cost, and its heat dissipation problem will inevitably be more difficult to solve. On the other hand, the development of LED products is not a slap in the face, and there are limits on development in each period. Products that fully meet the needs of use are on the market. For example, a single LED that is lower than the current one is not easy to be seen in the market. Therefore, if the existing LED products can improve their luminous intensity without causing problems such as increased heat generation and shortened life, There must be a need for it. SUMMARY OF THE INVENTION The human eye has the characteristic of persistence of vision, and the illuminant of high-frequency flicker will produce the illusion of continuous illumination. For example, if a fluorescent lamp (zinc light lamp) is driven by a transformer ballast, it will be Generates a flicker frequency twice the AC mains frequency (because there are two zero crossing points in a sine wave period), ie 6〇1^ mains will produce a 120Hz flicker frequency, which is still detectable by the human eye', Even if it has an adverse effect on the human eye, there is a higher-order luminaire to change the electronic ballast, and the power frequency is converted to a high frequency of about 1 〇 to 3 〇 ^. The flicker frequency is raised to 2 〇 嶋 , z, A high-frequency flash is beyond the scope of the human eye, and produces a continuous luminous visual effect. It is easy to say that for LEDs, it flashes off, but for the human eye, its 6 200950587 f is continuous illumination. The present invention utilizes this feature to apply a high-frequency switching discontinuous current to a plurality of LEDs or LED arrays, and to cause them to be sequentially turned off, and the current can be higher than the average forward current' or even the upper limit of the peak forward current. In order to increase the luminous intensity of the LED without increasing the heat generation of the LED, the cost of purchasing the higher power LED can be saved, and the heat dissipation problem that comes with it can be avoided. ❿【Embodiment】 Please refer to the first figure, which is the circuit block diagram of the invention, which is mainly composed of a pulse width modulation (PWM) generator (1) and a plurality of dimming constant current sources. (2a~2f) and a plurality of LED arrays (3 a~3 f), wherein the dimming constant current source (2a~2f) and the LED array (3 a~3 f) are the same number 'and a pair In a configuration, the figure is shown in the case of six groups, and of course, any other number other than one. On the other hand, the description here is made up of six LED arrays (3a~3f). An array, for example, if each LED array (3a~3f) is composed of one LED, the six LED arrays (3a~3f) will form a larger array with 60 LEDs, of course The single LK) array (3a~3f) can also be a single LED, with six LEDs forming an LED array. Another so-called dimming constant current source (2a~2f) refers to a DC constant current source with a PWM signal input terminal. The constant current output can be controlled by the PWM signal to generate a synchronous interrupt, such as the accumulation company (MACR0BL0CK). The MBI6650 DC-DC converter integrated circuit is produced, and the second leg dimming control 7 200950587 (pimming control terminal, DIM) can be used as the PWM signal input terminal. The PWM signal input terminals of the dimming constant current source (2a~2f) are respectively connected to the PWM signal output end of the PWM generator (1), and the PWM generator (1) can output the same number of PWM signals and output them separately. The timing of the PWM signal is shown in the second figure. Each group of PWM signals is periodic, and its period (T) and duty cycle (4) are the same, that is, the pulse period (r) of each PWM signal is the same. Assuming that the number of LED arrays (3a~3f) driven is η, the duty cycle d is the reciprocal of η, that is, d=l/n, and the pulse part® is sequentially connected in time, that is, one The pulse in a PWM signal is closely followed by a pulse of a second PWM signal. At the same time as the end of the pulse of the first PWM signal, the pulse of the second PWM signal occurs, and so on, assuming that the pulse period is 7:=lms And n=6, the period T of each PWM signal is equal to 6ms, and the duty cycle is d=l/6 and 16.67%. Each PWM signal is output to a corresponding dimming constant current source (2a~2f), so that the dimming constant current source (2a~2f) outputs a constant current driving power of the same timing as the input @PWM signal. To each of the LED arrays (3a to 3f), the LED arrays (3a to 3f) are caused to generate the same high-frequency sequential extinction as in the second figure, that is, the frequency of each single LED array (3a to 3f) is off. 1/THz, the overall dot-off frequency of all LEDs [3a~3f) is η/ΤΗζ. According to the above-mentioned figures, the frequency of each single LED array (3a~3f) is 166.7Hz, the whole The click-off frequency is 1 kHz. If the pulse period r of each PWM signal is set to 0.1 ms, the overall point-off frequency rises to 10 kHz; if r=0.05 ms, the overall point-off frequency will rise to 20 kHz; if τ: = At 0.0286ms, the overall point-off frequency will rise to 35kHz. 8 200950587 The present invention applies a plurality of LEDP trains (3a to 3f) with a high-frequency circulating point to a driving current higher than the rated average forward current of the LED, so that the instantaneous application intensity is increased, and the visual persistence characteristic of the human eye is utilized. So that "2 = luminous intensity forms a visual effect equivalent to continuous luminous intensity, and the overall brightness is improved.
以上說明僅為本發明之一較佳實施例之具體例示，並 非用以侷限本發明之專利範圍，其他熟習該項技藝之人所 可輕易完成之等效變換，均應俱屬下述之申請專利範圍。 【圖式簡單說明】 第一圖：本發明之電路方塊圖。 第一圖··本發明之PWM訊號時序圖。 【主要元件符號說明】 1··.脈寬調變產生器 ❹ 2a〜2f···調光式定電流源 3a〜3f·••LED 陣列The above description is only a specific example of a preferred embodiment of the present invention, and is not intended to limit the scope of the patent of the present invention. Other equivalents that can be easily accomplished by those skilled in the art are all applicable to the following applications. Patent scope. BRIEF DESCRIPTION OF THE DRAWINGS First FIG.: A block diagram of a circuit of the present invention. The first figure is a timing diagram of the PWM signal of the present invention. [Main component symbol description] 1··. Pulse width modulation generator ❹ 2a~2f···Dimming constant current source 3a~3f·••LED array