  A recent paper [1] (El Aroudi, 2012) misapplied a critical condition (Fang
and Abed, 2001) to a well-known example. Even if the mistake is corrected, the
results in [1] are applicable only to buck converters and period-doubling
bifurcation. Actually, these results are known in Fang's works a decade ago
which have broader critical conditions applicable to other converters and
bifurcations. The flaws in [1] are identified.
