A fast-response high power factor converter with a single power stage

An offline switching converter which operates with high input power factor while maintaining fast transient response at its output is described. A single power stage with dual output produces both the desired DC output and a boosting supply in series with the input. The resonant boosting supply at the input is controlled by frequency modulation of the power stage, while the desired DC output is PWM controlled. Since both the input boost supply and the output supply can be controlled independently, a fast transient response can be maintained at both the input (for active current wave-shaping), and at the output (for good output regulation). In addition, even without active control of the boost supply, a reasonably good input current waveshape results due to the natural gain characteristics of the boost resonant circuit. Zero voltage switching is maintained, allowing the circuit to be designed at high frequency to reduce size and cost, and increase performance