A switching signal generator for a switching power supply employing a DC-DC
modulator has an adder, an integrator and a quantizer. A gate driver
circuit is provided upstream of a power switch element and receives a
quantizer output. By feeding back a gate driver circuit output to the
adder of the .DELTA..SIGMA.-modulator, a large phase margin is obtained at
a high-frequency switching. The switching signal generator for the
.DELTA..SIGMA.-modulation type switching power supply has an improved
direct-current transmission linearity characteristic relative to
direct-current input, and that is stably controllable and of high
efficiency. Furthermore, a DC-DC converter has an adder, an integrator and
a quantizer, the integrator having a mechanism for adjusting its gain. The
gain-adjusting mechanism receives a signal from a current flowing
internally of the DC-DC converter, a voltage internally of the converter,
or a converter output voltage to control gain of the integrator so that
the amplitude of output voltage of the integrator is not saturated and a
comparator is capable of high-speed operation, a .DELTA..SIGMA.-modulation
type DC-DC converter is provided that is unlikely to undergo oscillation
especially at a high sampling frequency, and that produces a stable output
voltage.
