內建溫度感測及熱平衡機制的降壓轉換器設計

Abstract

本論文分析降壓轉換器之功率開關的整合型功率電晶體，即為多顆子功率電晶體所組成的功率電晶體串，其會因為電力線、負載線以及輸入輸出端的不同佈局會產生功率消耗的分佈不平均，而功率消耗較大的子功率電晶體所產生的熱也比較大，造成該子功率電晶體壽命下降，為了改善此問題，本論文提出了內建溫度感測及熱平衡機制來改善功率消耗分佈不平均的現象，達到整體功率電晶體溫度平衡。內建溫度感測利用RC Oscillator 之溫度感測器來測出每一顆子功率電晶體的溫度，先在校準模式中儲存各顆子功率電晶體初始溫度振盪的頻率次數，之後降壓轉換器開始運作時再逐一的偵測測試模式中各顆子功率電晶體的溫度，透過找尋最大上升溫的子功率電晶體電路，找尋出最大溫度的位址碼再傳入閘極端脈衝波調變電路進行脈波的調變動作，使最高溫度的子功率電晶體獲得短暫的休息使其得到溫度下降的目的，進而使得可靠度獲得提升。 本論文使用TSMC 0.25um製程，控制電路系統操作頻率為1MHz，晶片佈局面積為 。

This thesis analyzes combinative power MOS transistors, which are constructed by many small MOS transistors, in the power switch of buck converters. Depending on the layout between power line, the load and input/output of power switch, it has different distribution of power. When a small cell has large power dissipation, it produces more heat. The life of this small cell will be reduced. This thesis proposes a temperature sensing and thermal balancing mechanism to improve the reliability. The temperature sensor uses on RC oscillator to sense the temperature of each small cell. At first, the calibration mode stores each cell’s temperature. After buck converter is working, it measures each cell’s temperature again. Then, it searches the one with the highest temperature. A PWM modulation circuit takes off pulses from the transistor to reduce its duty cycle and lower the power dissipation. This chip is implemented in TSMC 0.25um process. The control system operates at 1MHz. The chip area is .