Reconfigurable bi-frequency DPWM with custom spectral shaping in a synchronous buck converter

Majority of spread spectrum techniques employ chaos-based PWM schemes in a switching power converter, in which neither dynamic performance nor ripple parameter can be correctly predicted so as for efficiency. This paper proposes a bifrequency DPWM controller which uses two discrete frequencies as guided by a modulating signal f_m(t). Fourier analysis shows that discrete frequencies only contribute to power spectrum at fundamental and harmonic contents of f_m(t). The controller can be easily reconfigured to achieve custom spread spectrum with predictable ripple parameters and insignificant performance impact. Discrete-time models are derived for stability analysis. Design guidelines are discussed for a synchronous buck converter. The proposed method has been implemented using an FPGA device.