Type II Compensator

Design Type II Compensation In A Systematic Way Liyu Cao, Ametek Programmable Power [email protected] Type II compensators are wiely use in t!e control loops "or power con#erters. A type II compensator !as two poles $one at t!e origin% an one &ero, an t!e &ero is place somew!ere between t!e poles. Designers use t!is type o" compensator to pro#ie a p!ase boost to t!e control loop. It is known t!at t!e compensator reac!es its ma'imum p!ase boost at t!e geometric mean o" t!e &ero(s "re)uency an t!e secon pole(s "re)uency. To es ign t!is type o" compensator, t!e popula r approac! is to pla ce t!e esire loop crosso#er "re)uency at t!e geometric mean o" t!e &ero an pole *+,-. T!is approac! can prouce ma'imum p!ase margin "rom a gi#en compensator. owe#er, it oes not take t!e ot!er important loop parameter, t!e ga in margin, into consieration. In general, to make a control loop work properly, it is necessary to !a#e bot! enoug! p!ase margin an gain margin, In t!is sense, it is important to !a#e a esign proceure t!at can take care o" bot! esign parameters. In t!is note, a systematic esign proceure is e#elope to esign a type II compensator, w!ic! gi#es t!e esigner an easy way to take bot! p!ase margin an gain margin into consieration an to a/ust t!e compensator until t!e esign re)uirement is satis"ie. + - OUT R1 R2 C1 C2 Vo Vi Figure 1. A type II error amplifier configuration using four passive components. Gain and phase characteristics. T!e sc!ematic o" a type II compensator is s!own in "igure +, w!ere "our passi#e circuit components are neee. T!e trans"er "unction o" t!e Type II compensator in "igure + is gi#en by % + $ + % $ , +, + + , , + + = = R sC s C R R sC v v s C i o Equation 1 w!ere C+ is t!e parallel combination o" C+ an C, +

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Type II Compensator