- 學位論文
用於改善過電流保護之電流模式控制轉換器
An Improved Over Current Protection for Current Mode Controlled Converter
摘要
UC384X 系列的IC是一個高效能定頻電流模式的控制轉換器，特別是應用在離線式DC/DC轉換器上。它以已經被使用超過二十年，他的積體電路功能包括了一個精確的且可微調責任週期的震盪器、增益誤差放大器、電流感測比較器以及一個圖騰輸出線路以驅動外部的功率MOSFET，它同時也具備了一個保護功能包括輸入及參考低電壓閂鎖遲滯功能，一個週期接一個週期的電流限制型之過電流保護功能，不幸的是，它需要許多的外部零件來達到良好的保護功能。 本論文乃在於研究一個在DC/DC轉換器上，具有鋸齒波限制以達到輸出過功率保護功能且無須輸入電壓補償電路的控制轉換器，這個控制轉換器當其偵測到外部電流訊號高於內部參考鋸齒波限制電壓的時候將會關閉其輸出，同時這個控制轉換器在DC-DC轉換器上，藉由縮短電流偵測訊號對控制轉換器輸出的延遲時間，而具有一個優越的過功率保護功能，而且這項功能將使得控制轉換器的外部零件更為精簡，同時因外部零件的減少而改善了DC-DC轉換器的平均間隔失效率(MTBF)。 本論文實際製作了一個5V/2A 的測試板，以實際的實驗波形及測試結果來驗證本文所提方法的可行性，而其結果是另人相當滿意的。
並列摘要
The UC384X series is a high performance fixed frequency current mode controllers especially design for off-line and DC−to−DC converter applications. It was used about two decades. Its integrated circuits feature a trimmed oscillator for precise duty cycle control, gain error amplifier, current sensing comparator, and a high current totem pole output for driving a power MOSFET. And it included a protective feature consisting of input and reference under-voltage lockouts each with hysteresis, cycle−by−cycle current limiting for output over current protection. Unfortunately, it needs to use lots of external circuits to achieve. In this thesis, a PWM controller has a saw-tooth limit for output power protection of DC-DC converter without input voltage compensation circuits is presented. This PWM controller will turn off its output when the current-sense signal of the PWM controller is higher than the reference saw-tooth limited voltage. At the mean while, this PWM controller has an excellent output power protection of DC-DC converter by a short delay time of current-sensing signal to its output. This feature makes external circuits of PWM controller simple and improves the mean time between failures (MTBF) of converter by decreasing part counts simultaneously. The experimental waveform and test result on a 5V/2A power board are shown to verify the feasibility of the proposal. The results are satisfactory.