In a controller for a DC to DC converter, PWM signal generating circuitry generates a set of PWM signals phase-shifted relative to one another, and controls states of the PWM signals according to a set of control signals. Each PWM signal of the PWM signals has an on-time state and an off-time state. Ramp signal generating circuitry, coupled to the PWM signal generating circuitry, generates a set of ramp signals having substantially the same ramp slope. Each ramp signal of the ramp signals is generated in response to detecting an on-time state of a corresponding PWM signal of the PWM signals. Additionally, a comparing circuit, coupled to the PWM and ramp signal generating circuitry, alternately compares the ramp signals with a preset reference to generate the control signals. A corresponding control signal of the control signals changes the corresponding PWM signal from the on-time state to an off-time state.