This paper presents an integrated power system for low-power wireless sensor networks with dynamic efficiency optimization technique. By adaptively resizing power transistors and adjusting switching frequency, system efficiency is enhanced significantly. Theoretical analysis is elaborated to support the proposed technique. A prototype integrated power system for self-powered photovoltaic wireless sensing node was designed and simulated with TSMC 0.35µm CMOS process. With a power range of 0.5µW

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... o 10mW, power efficiency stays above 71%. Tolerance between theoretical and simulated optimal power transistor sizes is less than 6.7%, while that of optimal switching frequencies is less than 5%. The paper gives another solution to minimizing system power in the perspective of power processing.