A synchronous switching voltage converter has a first switch, a second
switch, and an inductor, coupled together to a switch node. A reverse
current preventing circuit has a fixed reference current source, a
correcting circuit, a variable reference current generating circuit, and
a comparing circuit. Based on a comparison between an inductor current
and the fixed reference current source, the correcting circuit generates
a correcting signal. The variable reference current generating circuit
generates a variable reference current signal, which is adjusted in
accordance with the correcting signal. Based on a comparison between the
inductor current and the variable reference current signal, the comparing
circuit applies a preventing signal to the second switch so as to turn
off the second switch.