ارائه مدولاتور عرض پالسی مبتنی بر جهش فرکانس با هدف کاهش اسپور در مبدلهای کلیدزنی باک
محورهای موضوعی : مهندسی برق و کامپیوتررضا اینانلو 1 , امید شعاعی 2 *
1 - دانشگاه تهران
2 - دانشگاه تهران
کلید واژه: جهش فرکانسی, کاهش اسپور, مبدلهای کلیدزنی,
چکیده مقاله :
در این مقاله روشی جهت بهبود عملکرد طیفی و کاهش EMI مبدلهای باک مبتنی بر روش کلیدزنی ارائه شده و این کار با به کارگیری تکنیک جهش فرکانسی در قسمت مدولاتور انجام گردیده است. به این منظور یک مدولاتور عرض پالسی آسنکرون (APWM) با قابلیت جهش فرکانسی پیشنهاد شده است. از آنجایی که این نوع مدولاتور ذاتاً دارای رفتار خودنوسانی بوده و فرکانس نوسان آن وابسته به تأخیر حلقه آن میباشد، از این خاصیت جهت تغییر فرکانس نوسان آن استفاده شده است. به طوری که با تغییر تصادفی تأخیر حلقه آن بین 8 مقدار تصادفی، فرکانس خودنوسانی آن نیز بین 8 مقدار متفاوت تغییر یافته و در نتیجه طیفی بدون اسپور در خروجی آن ایجاد میشود. رفتار مدولاتور بر اساس مدل سیستمی به کمک روابط ریاضی تجزیه و تحلیل شده و سپس صحت این روابط به صورت رفتاری توسط نرمافزار Simulink-Matlab بررسی گردید. با توجه به این که در روش پیشنهادی عمل جهش فرکانسی در بخش دیجیتال مدولاتور انجام میشود، کنترل فرکانس به مراتب سادهتر از روشهای ارائهشده در کارهای قبلی است. همچنین لازم به ذکر است که بزرگترین مزیت روش پیشنهادی در مقایسه با سایر روشهای گسترش طیفی، پیوستگی سیگنال حامل آن به هنگام جهش فرکانس میباشد.
This paper presents an EMI reduction technique for switched-mode buck converters. To achieve this, the frequency hopping concept is utilized in asynchronous pulse width modulators (APWM) performing the power conversion with controlling the on-off time of the power switches. The modulator has an oscillatory behavior; such that its oscillation frequency depends on its internal loop delay. Making use of this property and randomly changing the loop delay between 8 distinct random values, its self-oscillation frequency is also changed between 8 different values. As a result, a spur-free spectrum is achieved at the output of the converter. To verify the usefulness of the proposed method, a model-based behavioral simulation was done using MATLAB-SIMULINK. The main advantage of the proposed method over previous works is that the switching frequency controlling mechanism is fully digital. Besides, it can be readily done without causing any disturbance in the carrier signal.
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