降低寄生元件效應的固定導通時間控制於使用陶瓷電容的降壓電源轉換器

Abstract

近年來隨著可攜式產品的需求逐漸增加，用來提供可攜式產品系統電源且具有小體積以及高效能的電壓穩壓器變得越來越重要。實際應用中固定導通時間控制法的電壓穩壓器常被使用，因為具有幾項優點，如系統結構簡單、快速暫態反應，以及在輕負載時具有高效率的優點。一般來說，固定導通時間控制法的穩壓器是利用輸出端訊號的漣波來穩壓，基本上須使用較大等效串聯電阻的輸出電容才可有效控制系統。由於低成本的優勢，積層陶瓷電容目前被廣泛的使用於消費性電源管理晶片，但是積層陶瓷電容的等校串聯電阻卻很小。在傳統的控制法使用具有小等效串聯電阻的輸出電容時，由於輸出端訊號的漣波幾乎僅有電容的成分，故漣波很小系統易受雜訊影響。 因此，本文提出新的固定導通時間控制法電壓穩壓器架構，可提高雜訊容限寬度，可消除輸出電容上的等效串聯電感及小等效串聯電阻效應。並且由於導通時間可隨輸入及輸出電壓調整，操作在連續導通模式時的系統切換頻率可以在廣泛的輸入電壓裡維持幾乎定值。模擬結果顯示出輸出電壓漣波維持約 2mV，在負載變動範圍為0到600mA 時。此時使用的等效串聯電阻小於5mΩ。

In recent years, with the increasing demand of portable products, used to provide system power of portable products with small size and high performance voltage regulator becomes more and more important. Constant on-time control regulators are preferred in practice for several important advantages, such as simple system structure, fast response time and high efficiency for light load. In general, constant on-time control regulators regulate their output voltage based on the ripple component in the output signal. Basically, requires the use of large equivalent series resistance (ESR) of the output capacitance can be effectively controlled system. As a low-cost advantage, multilayer ceramic capacitors (MLCC) are widely used in consumer power management chip, but its equivalent series resistance is very small. In conventional constant on-time control with small ESR value on the output capacitor, the regulator is easily affected by the noise due to small output ripple, which is dominated by the ripple on the output capacitor. Therefore, this paper proposes new constant on-time control regulator structure can improve the noise margin, to eliminate the equivalent in series inductance (ESL) and the small equivalent series resistance (ESR) effect. Furthermore, since the on-time period is set simply by input and output voltages, the switching frequency in continuous conduction mode (CCM) operation is relatively constant over a wide input voltage range. Simulation results show that the output ripple keeps around 2mV, when load current step is 600mA and ESR is smaller than 5mΩ.