使用低等效串聯電阻之輸出電容的快速暫態響應電壓平方控制直流/直流降壓轉換器

Abstract

由於高效能可攜式電子產品的快速發展，電壓轉換器的暫態響應的也更加重要。系統需要一個在參考電壓和負載變化時有快速動態響應的電壓轉換器來減少閒置和工作模式之間切換的等待時間和節省電池能量。因此，一個具有快速暫態響應且使用低等效串聯電阻之輸出電容的電壓平方控制降壓轉換器在本論文中提出。

在傳統的電壓平方控制方式中，須使用具有較大等效串聯電阻之輸出電容來達到快速暫態響應，此外傳統架構還會造成參考電壓追隨速度非常緩慢的問題。因此在本論文中，透過對輸出電壓漣波微分後萃取出電感電流訊息，即使在低等效串聯電阻之輸出電容條件下也能獲得電感電流資訊，維持電壓平方控制方式的快速暫態響應特性。利用電壓控制電流源電路取代傳統運算放大器型微分器對輸出電壓微分，能減少晶片面積和功率消耗。且由於電壓控制電流源電路輸出訊號的直流位準與降壓轉換器之輸出電壓直流位準無關，因而能大幅改善電壓平方控制方式的參考電壓追隨速度。

本篇論文以台灣積體電路製造股份有限公司點三五微米互補式金氧製程來實現此高效能的快速暫態響應電壓平方控制直流/直流降壓轉換器，其切換頻率為1 MHz，使用具有等效串聯電阻30 mΩ的輸出電容4.7 μF，對負載450 mA變化的回復時間約5 μs; 在輸出電壓變化0.5 V情況下，對參考電壓變化的響應時間小於15 μs。其快速動態響應之特性在本論文中以模擬結果驗證。

Due to the rapid development of high performance portable electronic equipment, voltage converter has drastically increased the importance of transient response. Frequent supply voltage and load current switching between the idle mode and the active mode for conserving the battery energy requires the converters have faster dynamic responses in reference tracking and load transient to reduce latency. Therefore, a fast transient response V2 control buck converter with low ESR capacitor is proposed in this thesis.

The conventional V2 control scheme suffers the problem of slow reference tracking speed and relying on large equivalent series resistance (ESR) of output capacitor for achieving fast transient response. In this thesis, the adopted method of extracting the inductor current message through differentiating output voltage ripple can maintain fast transient response in V2 control structure even with low ESR capacitor. Using voltage-controlled current source circuit instead of op-amp-based differentiator to differentiate output voltage can reduce the production cost. Besides, the dc-voltage of VCCS-based differentiator output is not influenced by dc-voltage of converter output that can improve reference tracking speed of V2 control method significantly.

The high performance V2 control dc-dc buck with faster dynamic responses is implemented by TSMC 2P4M 0.35-μm CMOS technology. The constant switching frequency is 1MHz and output capacitance is 4.7 μF with 30 mΩ ESR. The load transient recovery time is around 5 μs under 450 mA load step and reference tracking response time is less than 15 μs with 0.5 V output voltage Vo change. Fast dynamic response is achieved and demonstrated by simulation results in this thesis.