Apparatus for improving stability and dynamic response of half-bridge converter

Abstract

Typically, in a half-bridge converter A DC blocking capacitor and inductance on the primary side combines with the inductor and capacitor on the secondary side to produce complicated converter dynamic characteristics that make converter stabilization difficult. The disclosed system and methods enable converter stabilization by modulating, as a function of the voltage across the DC blocking capacitor, the feedback output error signal or the ramp signal for the PWM controller of the converter. The modulation removes the effect of the resonant circuit formed by the primary inductance and the DC blocking capacitor in the output voltage regulation loop. Further adjustment of the duty cycle of the power switches enables keeping the output voltage undisturbed by voltage variation across the DC blocking capacitor. Since, this inner compensation loop results in the voltage regulation feedback loop respond to only the output inductor-capacitor filter, the transfer function of this loop displays second order characteristics from the fourth order. Hence, stability issues are simplified to conventional second order compensation network whereby the converter can be optimized for fast transient response.