Small-Signal Analysis and Design of Constant Frequency V2 Peak Control (1)
Constant frequency V2 peak control is widely researched in literature and used in industry in DC-DC converters due to its simple implementation and fast transient response. However, the effect of the capacitor voltage feedback needs to be clarified for design purposes. This nugget analyzes the small-signal model for constant frequency V2 peak control. There are two pairs of double poles located at ½ fsw in this control structure because of two kinds of feedback information. First, the sidebands of the inductor current information cause a sample-and-hold effect resulting in one pair of double poles located at ½ fsw. Next, the sidebands of the capacitor voltage information cause another pair of double poles located also at ½ fsw. The Instability issue occurs not only in a large duty cycle case, but also in the case with small capacitor time constants.