AN012 Datasheet, PDF (1/7 Pages) Analog Intergrations Corporation – Buck Converter

AN012
A Handy Method to Obtain Satisfactory Response of
Buck Converter
Introduction
The focus of this application note is to help users to
select a good set of components of the compensation
section of the Buck converter. Traditionally, engineers
first concern about the power circuit for a circuit design.
After meeting the power requirement, what follows is
control loop design. The first priority of control design is
the stability. And after that, the choice of components
can substantially effect the transient response. Here
shows a simple method to obtain a satisfactory
transient response with an acceptable steady state
error.
Analysis:
Fig.1 shows the unity feedback system for Buck
converter. We first identify transfer functions for each
of the corresponding block.
As to the modeling of the low-frequency behavior of
power switches in square-wave power converters,
please refer to appendix [1]. The circuit of Buck
converter is shown in Fig.2 and the model of its power
switches is shown in Fig.3. Please note that the circuit
in Fig.3 is linear. Fig.4 shows the circuit for small signal
analysis.
+
dV_OUT(s)=0 _
Gc(s)
PWM
Gp(s) ^dVOUT(s)
dVc(s)
dD(s)
Fig.1 The Unity Feedback Control Loop for Buck Converter
R1
VIN
R2
VOUT
+
Fig. 2 Buck Converter
October, 2001
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