A power detection circuit has a first comparator block, a charge controller block, and a second comparator block. The first comparator block compares a supply voltage with a first threshold value, and the charge controller block controls the charging of a first capacitor according to an output signal of the first comparator block. The second comparator block compares the charge in the first capacitor with a second threshold value so as to produce a power detection signal, and wherein a second capacitor is interposed between the charge controller block and the first capacitor.