A control circuit is incorporated in a switching regulator for monitoring
and maintaining a bootstrap voltage to allow the switching regulator to
operate at or near 100% duty cycle. The control circuit includes a
circuit receiving the bootstrap voltage and generating a monitor voltage,
a comparator circuit receiving the monitor voltage and a first voltage
indicative of a switching output voltage and generating an output signal
having a first state when the monitor voltage is equal to or less than
the first voltage, a logic circuit receiving the output signal and
generating drive control signals to driver circuits driving the high-side
and low-side power switches. The logic circuit generates the drive
control signals in response to the output signal of the comparator
circuit having the first state to cause the high-side power switch to
turn off and the low-side power switch to turn on, thereby recharging the
bootstrap voltage.