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This paper presents a power management unit (PMU) for emerging applications powered by low-voltage single direct methanol fuel cell (DMFC). A subthreshold startup scheme and its circuit implementation are proposed to enable low-voltage self-startup feature. A boost switching converter with a switch-mode, quasi-V2 hysteretic control is designed for power conditioning. The PMU is implemented on a standard 0.35-μm CMOS process with VTN/VTP of 0.55 V/ -0.75 V, respectively. Experimental results prove that the PMU automatically starts up with 450-mV single DMFC input. The output voltage of the PMU is well regulated with below 25 mV ripple. With an output power ranging from 20 to 200 mW, an average efficiency above 85.2% is obtained, with a maximum of 89.4%. Load transient recovery times are 11.6 μs/4.2 μs, respectively, in response to the step-up and step-down load changes between 10 and 100 mA.
Date of Publication: Sept. 2012