9

TYPE II LOOP COMPENSATION DESIGN

Type II compensation is specifically used when an Electrolytic or Tantalum output

capacitor is chosen at the converter output due to its low cost. In that case, the zero

caused by the output capacitor ESR is within a few khz and this is of course greatly

simplifying the voltage loop compensation design. By adding an additional zero in the

compensation loop before the first pole, the voltage loop bandwidth is extended with a

90º phase boost and hence the overall transient response time is improved. Most

previous guidelines for calculating the component values for Type III compensation can

be carries over for Type II except for the new Rz, Cz and Cp components. Note that

Rz2, Cz2, Cp1, Rz3, and Cz3 components are not required for the Type II Loop

Compensation Design.

Figure 14. Voltage Mode Control Loop with Loop Dynamic for Type II Compensation