Small-signal modeling of variable-frequency pulsewidth modulators

Small-signal linear models are presented for variable-frequency constant on-time and variable-frequency constant off-time pulsewidth modulators. Both modulation methods are shown to have leading phase characteristics and nonlinear amplitude responses. The analytical results are validated by numerical simulation results and compared with previously published empirical models. The models are intended for use in analysis and control design of pulsewidth modulated switching power converters.