201218590 六、發明說明： 【發明所屬之技術領域】 本發明相關於一種電源轉換器之控制電路，尤指一種可抖動切 換頻率之電源轉換器之控制電路。 【先前技術】 交換式電源轉換器具有高效率、低耗損、小尺寸及重量輕等優 點，因此已被廣泛地用以作為各種電子產品的電源轉換裝置。 請參考第1圖，第1圖為先前技術之電源轉換器之示意圖。電 源轉換器101包含控制電路102、功率開關1〇3、變壓器1〇4以及回 授電路105。變壓器120包含初級線圈NP、次級線目Ns以及辅助 線圈NA，變壓器之初級線圈Np電性連接於輸入電壓源viN以及 功率開關103 ’變壓器之輔助線圈να可提供電壓源vCC給控制電 路102’變壓器之次級線圈Ns經由二極體1〇6對電容1〇7充電以提 供輸出賴VOUT，輸$賴V〇UT將㈣回授電路1G5之訊號 處理以產生回授成號給控制電路川2。一般而言，控制訊號之 工作頻率係大致由控制電路1〇2根據流經外接之電流設定電阻^ 的頻率蚊電流If所蚊。已知交換電源供絲會於交翻率之諧 波中央處產生頻率發射電磁干擾(EMI)或射頻干擾(亿^)。 父換式電源轉換器利用切換電源技術縮減了交換式電源轉換 201218590 =體積’ _切換電源技術可缩減交 部也因交換式電源轉換器的主動 =轉換器的體積，但 ，電源及其周邊設備，交干擾，而 電磁干擾m置，例如電磁干m波器、龍轉=要配置降低 類防電磁讀触魏造成姆 ^'財。然而，此 轉換器的成本與體積。 力羊她，相對增加交換式電源 【發明内容】 因此，本發明 換器之控制電路。 之-目的在於提供—種可抖杨_率之電源轉 =發明係提供-種電源轉換器之控制電路，包含 一讀顧單元一輸__元、,器= 早疋、 :頻!抖動單?:該時序單元用來根據-反咖產生二 μ “緣遮蔽單調來產生—輸出電流之偵測魏。該輸 &控制單㈣來根據—回授電壓產生—輸出電流之 較f性連接_輸出紐控卿元錢該前緣輕單元，用= ^雨出電w之制賴與該輸出電流之參考電壓進行比較，以產生 一截止訊號。該SR正反器具有一設定(s_電性連接於該時序單 兀，一重設(RESET)端電性連接於該比較器，以及—輸出端，用來 根據賴止峨以及料通訊號產生—驅動減。該醉抖動單元 電連接於該輸出電流控制單元，用來根據該驅動訊號調整該輪出 電流之參考電壓。 6 201218590 元° _序單元用來根據 T時間產生—導通訊號。該前緣賴單朗來產生-輸出電、、，之 >=ΓΠΓ制單元用來根據-回_產生-_ :參!賴。舰較器電性連接於該輸出電流㈣單元以及該前 1:=，’用來縣輪出電流之制電壓與該輸出電流之參考電 仃，以產生一戴止訊號。該SR正反器具有一設定(犯 電性連接於辦料元，—重設比較器， 口以及-輸出端，时根據賴止·以及料軌號產生—驅動訊 號。該醉抖解元電性連接於_序單元，时根獅驅動訊號 調整該最小關閉時間。 【實施方式】 請參考第2圖，第2圖為本發明之電源轉換器之第一實施例之 示意圖。在本發明之實施例中，電源轉換器以返馳式(flyback)電源 轉換器作說明。電源轉換器201包含控制電路200、功率開關2〇3、 變壓器204以及回授電路205。變壓器204包含初級線圈Np、次級 線圈NS以及輔助線圈NA，變壓器之初級線圈NP電性連接於輸入 電壓源VIN以及功率開關203，變壓器之次級線圈Ns經由二極體 206對電容207充電以提供輸出電壓VOUT，回授電路2〇5根據輸 出電壓VOUT產生回授電壓VFB給控制電路200,變壓器之輔助線 201218590 圈ΝΑ可提供電壓源以及變壓器之反射電壓VR給控制電路2〇〇。 控制電路200用來控制功率開關2〇3之導通以及截止。本發明之控 制電路200可抖動功率開關2〇3之切換頻率，以改善電磁干擾之現 象。 徑制％路2〇〇包含時序單元2U、前緣遮蔽(leadingedge blanking，LEB)單元22卜輸出電流控制單元222、比較器223、级 正反器231、緩衝器232以及頻率抖動單元24〇。時序單元211根據 反射電壓VR產生導通訊號s〇N。前緣遮蔽單元221電性連接於功 率開關203，以產生輸出電流之備測電壓。輸出電流控制單元222 根據回授電壓VFB產生輸出電流之參考賴。比㈣223將輸出電 流之_電壓與輸出電流之參考電壓進行比較，以產生截止訊號 SOTF。SR正反器231具有設定(SET)端、重設印端以及輸出 端’ SRJL反益231之設定端電性連接於時序單元叫，sr正反器 231之重設端電性連接於比較器223，犯正反器231根據截號 S〇FF以及導通訊號S0N產生驅動訊號咖。緩翻说電性連接 於SR正反器23i之輸出端以及功率開關2〇3之間，用來加強驅動 訊號請，並根據驅動訊號SDV驅動功率開關2〇3。功率開關撕 之切麵料導通峨隨狀鼓峨s〇ff之職和之倒數， 其中導通織SON根據反射電壓VR職生，截止訊號咖是由 比較輸出電流之_電壓與輸出電流之參考電壓而產生。頻 單_電性連接於輸出電流控制單元222，可根據驅動訊號咖 調整輸出電流之參考電壓，達到抖動功率開關加之切換頻率之目 201218590 的。 頻率抖圖’第3圖為第2圖之解抖鮮元之魏方塊圖。 數_ I:包含咖241、_242以_器243。計 號請之週期時間時增加計數，^十數H數謂在驅動訊 用决⑽—▲ 七加找4數大於4時歸〇。查找表242 安/ Γ母3十數所對應之抖動值，當計數器241產生計數後，頻 。抖動早70 240由查找表242中找到該計數所對廣 如 m晴狀抖動值，例如， 最小的調整單位數值==:=2d，其中d為 =調整的輸_之參考電壓VAm二電:參考 之參考電壓進行算術運算，例如將抖動值與輸出電二 相加或相減。因此，比較器奶根據調整的輸出電流之參 率門所產生域止峨SOTF之辭會残律的變動，功 3之切換頻率也因為截止訊號SOFF而抖動。 -立请參考第4圖’第4圖為本發明之電源職器之第二實施例之 。在第—實施例中，控制電路調整截止訊號猶來抖 $功率開關203之切換頻率，在第二實施例中，控制電路4 ^號謂來抖動功率開關2G3之切換頻率。控制電路锡包含 4〇早疋41卜前緣遮蔽單元42卜輸出電流控制單元422、比較器 sot 反器43卜緩衝器432以及頻率抖動單以4G。導通訊號 根據變壓益204之反射電壓VR所產生，時序單元4ιι接收變 201218590 壓器之反射電壓後，柄诚 最小關閉時間之長度與^關閉時間來產生下一個導通訊號。 一參者雷祕 、。&電堅卿有關，當回授賴VFB大於 參考電壓時小關閉時間為固定長度，當回授電壓VFB小於該 最小關閉時間會隨著回授電壓的減小而增加。頻率抖 ===所，—導通 導通訊號SON而抖動。’功率開關加之切換頻率也因為 頻率5 _ 5 _ 4社_鮮㈣能方塊圖。 數Hr包含計數器441、查找表442以及調整器443。計 數_根據驅動訊號SDV產生計數，例如 =爛_冑壤，細切。查 母-計數所對應之抖動值，當計數器441產生計數後，頻 元_由查找表442 t找到該計數所對應之抖動值，例如， ^數為3時，可由查找表442找出所對應之抖動㈣，其中d為 調整單位數值。調整器443可根據抖動值與最小關閉時間產 ”的最小關閉時間TADJ。調整器443將抖動值與最小闕閉時 間進行ΐ術運算，例如將抖紐與最小_時_加或相減。因此， 比較器423根據織的最州_間簡所赵之導通訊號腦 之頻率會不規律的變動，功率開關2〇3之切換頻率也因為截止訊號 SON而抖動。 前緣遮 綜上所述，電源轉換器之控制電路包含一時序單元、 201218590 蔽單元、-輸出電流控制單元、一 率抖動單元。#_ σ 正反器以及一頻 =J單元產:Γ 小_時間產生-導通訊號。該 诚一 η沪啻厭^ 制電壓。錢出電流控制單元根 據-龍電[產生-輸出電流之參考電壓。 偵測電顯輸㈣流之參考龍進触較，以產= 參考龍以改變該截止訊號，或 口周正s亥最小關閉時間以改變該導 ㈣以料道、Sw 亥狄正反器根據該截土 减以制導柄缝生㈣1_之軸峨。因此，本發 明之電源雜k控制電路可柄功相狀切 磁干擾之現象。 f 以上所述僅為本發明之錄實施例，凡依本發 所做之鱗·與_1闕本發狀涵蓋範圍。 【圖式簡單說明】 第1圖為先前技術之電源轉換器之示意圖。 第2圖為本發明之電轉換iiH施例之示意圖 第3圖為第2圖之頻率抖動單元之示意圖。 第4圖為本發明之電源轉換ϋ之第二實施例之示意圖。 第5圖為第4圖之頻率抖動單元之功能方塊圖。 【主要元件符號說明】 電源轉換器 101 ' 201 Λ 401 201218590 102、200、400 控制電路 103 、 203 功率開關 104 、 204 變壓器 105 、 205 回授電路 106 、 206 二極體 107 、 207 電容 211 ' 411 時序單元 221 、 421 前緣遮蔽單元 222 ' 422 輸出電流控制單元 223 ' 423 比較器 231 、 431 SR正反器 232 、 432 緩衝器 240、440 頻率抖動單元 241 、 441 計數器 242 、 442 查找表 243 、 443 調整器 NP 初級線圈 NS 次級線圈 ΝΑ 輔助線圈 VIN 輸入電壓源 VOUT 輸出電壓 VR 反射電壓 12 201218590 VFB 回授電壓 SON 導通訊號 SOFF 截止訊號 SDV 驅動訊號 13201218590 VI. Description of the Invention: [Technical Field] The present invention relates to a control circuit for a power converter, and more particularly to a control circuit for a power converter capable of dithering a frequency. [Prior Art] The switching power converter has advantages such as high efficiency, low loss, small size, and light weight, and thus has been widely used as a power conversion device for various electronic products. Please refer to FIG. 1 , which is a schematic diagram of a power converter of the prior art. The power converter 101 includes a control circuit 102, a power switch 1〇3, a transformer 1〇4, and a feedback circuit 105. The transformer 120 includes a primary coil NP, a secondary line Ns, and an auxiliary winding NA. The primary winding Np of the transformer is electrically connected to the input voltage source viN and the power switch 103'. The auxiliary coil να of the transformer can provide a voltage source vCC to the control circuit 102'. The secondary winding Ns of the transformer charges the capacitor 1〇7 via the diode 1〇6 to provide the output VOUT, and the output of the circuit 4G5 is sent to the control circuit. 2. In general, the operating frequency of the control signal is substantially determined by the control circuit 1〇2 according to the frequency of the current flowing through the external setting resistor ^. It is known that the switching power supply wire generates frequency emission electromagnetic interference (EMI) or radio frequency interference (100 million) at the center of the harmonic of the turnover rate. The parent-changing power converter utilizes switching power technology to reduce the switching power conversion 201218590 = volume ' _ switching power technology can reduce the cross section also due to the active power of the switching power converter = converter, but the power supply and its surroundings Equipment, cross interference, and electromagnetic interference m set, such as electromagnetic dry m wave, dragon turn = to configure to reduce the class of anti-electromagnetic reading Wei Wei ^ ^ Cai. However, the cost and volume of this converter. She is relatively strong in switching power supply. SUMMARY OF THE INVENTION Therefore, the control circuit of the converter of the present invention. The purpose is to provide a kind of shuffling Yang _ rate power supply = invention system provides a kind of power converter control circuit, including a reading unit, a loss __ yuan, device = early 疋, : frequency! ?: The timing unit is used to generate the output current detection according to the anti-coffee generation two μ "edge mask monotony. The output & control unit (four) to according to - feedback voltage generation - output current of the f-connection _ output New Zealand control yuan money the leading edge light unit, with = ^ rain power supply w is compared with the reference voltage of the output current to generate a cutoff signal. The SR flip-flop has a setting (s_ electricity) Connected to the timing unit, a reset (RESET) terminal is electrically connected to the comparator, and an output terminal is configured to generate a drive subtraction according to the dependency and the material communication number. The drunk jitter unit is electrically connected to the The output current control unit is configured to adjust the reference voltage of the wheel current according to the driving signal. 6 201218590 元° The sequence unit is used to generate a communication number according to the T time. The leading edge is generated by a single output. , >=ΓΠΓ unit is used to generate according to -back_ -_ : 参! 赖. The ship is electrically connected to the output current (four) unit and the first 1:=, 'the voltage used to generate the current from the county and the reference current of the output current to generate a wear The SR flip-flop has a setting (the electrical connection is made to the processing unit, the comparator, the port and the output are reset, and the driving signal is generated according to the Lai and the track number.) Electrically connected to the _ sequence unit, the time lion driving signal adjusts the minimum closing time. [Embodiment] Please refer to FIG. 2, which is a schematic diagram of a first embodiment of the power converter of the present invention. In the embodiment, the power converter is described by a flyback power converter. The power converter 201 includes a control circuit 200, a power switch 2〇3, a transformer 204, and a feedback circuit 205. The transformer 204 includes a primary coil Np. The secondary winding NS and the auxiliary winding NA are electrically connected to the input voltage source VIN and the power switch 203, and the secondary winding Ns of the transformer charges the capacitor 207 via the diode 206 to provide an output voltage VOUT. Power 2〇5 generates a feedback voltage VFB according to the output voltage VOUT to the control circuit 200, and the auxiliary line 201218590 of the transformer can provide a voltage source and a reflected voltage VR of the transformer to the control circuit 2. The control circuit 200 is used to control the power switch 2 The turn-on and turn-off of the 〇3. The control circuit 200 of the present invention can dither the switching frequency of the power switch 2〇3 to improve the phenomenon of electromagnetic interference. The path %2 includes the timing unit 2U, leading edge blanking (leading edge blanking, The LEB) unit 22 outputs an output current control unit 222, a comparator 223, a stage flip-flop 231, a buffer 232, and a frequency dithering unit 24A. The timing unit 211 generates a pilot communication number s〇N based on the reflected voltage VR. The leading edge shielding unit 221 is electrically connected to the power switch 203 to generate a standby voltage of the output current. The output current control unit 222 generates a reference of the output current based on the feedback voltage VFB. The ratio (IV) 223 compares the voltage of the output current with the reference voltage of the output current to generate a cutoff signal SOTF. The SR flip-flop 231 has a set (SET) terminal, a reset print terminal, and an output terminal. The set terminal of the SRJL counter- benefit 231 is electrically connected to the timing unit, and the reset terminal of the sr flip-flop 231 is electrically connected to the comparator. 223. The flip-flop 231 generates a driving signal according to the truncation number S〇FF and the communication number S0N. The electrical connection is electrically connected between the output of the SR flip-flop 23i and the power switch 2〇3 to enhance the driving signal, and the power switch 2〇3 is driven according to the driving signal SDV. The power switch tears the cut fabric to turn on the 峨 峨 峨 之 之 之 之 之 之 之 之 之 , , 其中 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据 根据produce. The frequency single_ is electrically connected to the output current control unit 222, and the reference voltage of the output current can be adjusted according to the driving signal to achieve the purpose of the jitter power switch and the switching frequency of 201218590. The frequency jitter diagram is shown in Fig. 3 as the Wei block diagram of the debounced fresh element in Fig. 2. Number _I: contains coffee 241, _242 to _ 243. When counting, please increase the count in the cycle time. ^The number of H is said to be in the drive. (10)—▲ Seven plus find 4 when the number is greater than 4. Look for the jitter value corresponding to the table 242 amp / Γ mother 3 tens, when the counter 241 generates a count, the frequency. The jitter is early 70 240. The lookup table 242 finds the wide and m-like jitter value of the count, for example, the smallest adjustment unit value ==:=2d, where d is = the adjusted reference voltage VAm: The reference voltage is referenced for arithmetic operations, such as adding or subtracting the jitter value from the output power. Therefore, the comparator milk stops the change of the rhythm of the SOTF based on the parameter of the adjusted output current, and the switching frequency of the power 3 is also shaken by the cutoff signal SOFF. - Please refer to Fig. 4'. Fig. 4 is a second embodiment of the power supply unit of the present invention. In the first embodiment, the control circuit adjusts the switching frequency of the power switch 203 by the cutoff signal. In the second embodiment, the control circuit 4^ refers to the switching frequency of the power switch 2G3. The control circuit tin includes 4 〇 41 前 leading edge shielding unit 42 卜 output current control unit 422, comparator sot counter 43 buffer 432 and frequency jittering unit 4G. The communication number is generated according to the reflected voltage VR of the variable voltage benefit 204. After the timing unit 4 ιι receives the reflected voltage of the 201218590 voltage, the length of the minimum closing time and the closing time of the handle are used to generate the next communication number. One of the participants is secret. & Dian Jianqing, when the feedback VFB is greater than the reference voltage, the small closing time is a fixed length. When the feedback voltage VFB is less than the minimum closing time, it will increase as the feedback voltage decreases. The frequency jitter ===, - the conduction signal SON is dithered. The power switch plus the switching frequency is also due to the frequency 5 _ 5 _ 4 _ fresh (four) energy block diagram. The number Hr includes a counter 441, a lookup table 442, and a adjuster 443. Count _ generates a count based on the drive signal SDV, for example = rotten _ 胄 ,, fine cut. The jitter value corresponding to the check-count is counted. After the counter 441 generates the count, the frequency__ finds the jitter value corresponding to the count by the look-up table 442t. For example, when the number is ^3, the corresponding table 442 can be used to find the corresponding value. Jitter (four), where d is the adjustment unit value. The adjuster 443 can generate a minimum off time TADJ according to the jitter value and the minimum off time. The adjuster 443 performs the trick operation on the jitter value and the minimum lockout time, for example, adding or subtracting the jitter and the minimum_time. The comparator 423 varies according to the frequency of the brain of the state of the state, and the switching frequency of the power switch 2〇3 is also shaken by the cutoff signal SON. The control circuit of the power converter comprises a timing unit, a 201218590 shielding unit, an output current control unit, a rate dither unit, a #_ σ flip-flop and a frequency=J unit: Γ small _ time generation-guide communication number. Chengyi η 啻 啻 啻 制 制 制 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱 钱The cutoff signal, or the minimum closing time of the mouth is changed to change the guide (4) to the feedway, and the SwHide flip-flop is subtracted from the guide by the stem (4) 1_. Therefore, the power supply of the present invention is mixed. Control circuit can handle the phase The phenomenon of magnetic interference f. The above is only the recorded embodiment of the present invention, and the scales and _1 阙 according to the present invention cover the scope of the present invention. [Simple description of the drawing] FIG. 1 is a power conversion of the prior art. 2 is a schematic diagram of a power conversion iiH embodiment of the present invention, FIG. 3 is a schematic diagram of a frequency dithering unit of FIG. 2. FIG. 4 is a schematic diagram of a second embodiment of a power conversion port of the present invention. Figure 5 is a functional block diagram of the frequency dithering unit of Figure 4. [Main component symbol description] Power converter 101 '201 401 401 201218590 102, 200, 400 Control circuit 103, 203 Power switch 104, 204 Transformer 105, 205 Feedback circuit 106, 206 diode 107, 207 capacitor 211 '411 timing unit 221, 421 leading edge shielding unit 222 '422 output current control unit 223 '423 comparator 231, 431 SR flip-flop 232, 432 buffer 240 440 frequency jitter unit 241, 441 counter 242, 442 lookup table 243, 443 adjuster NP primary coil NS secondary coil 辅助 auxiliary coil VIN input voltage Output voltage VR reflected voltage VOUT 12 201218590 VFB feedback voltage turn-on signal SON off signal SOFF drive signal SDV 13