AN021 datasheet(6/7 Pages) AIC

6 / 7 page

AN021

October, 2001

R2C3=

250k

……………… . C3=7.14

≈ 8p

Fig.12

The Transient Response

(Ch2 is current curve, 1A/div)

Fig.13

The Corresponding Simulation of

Frequency Response

Referring to Fig. 13, the crossover frequency of open

loop transfer function is raised. And we could also

expect the bandwidth of the closed loop transfer

function being increased. Indeed, in Fig 12, the set of

control components, which we just used, shows high

speed of response and less overshoot.

Although the pole at origin (according to equation (5))

means the infinitive gain at DC (

ω=0), it is still a good

idea to verify the steady state error by the load

regulation. From Fig.12, it shows that the steady state

error of two settings is small, and the two curves are

almost identical.

4.9

4.95

5.05

5.1

Iout(A)

C2=820p R2=560k

C3=8p

C2=6800p R2=75k

C3=56p

Fig.14

The Comparison of Load Regulation of

Different Components (VIN=8V, VOUT=5V)

From the results of transient response and the steady

state error, the second set of components can achieve

a satisfactory response.

Summary

By taking the advantage of a high gain at low

frequency with a low gain at high frequency, the

best performance of the Buck Converter can be

achieved. The objectives are to improve the steady

state error at low frequency and reduce noise

disturbance at high frequency.

The key points of the compensation are:

1) Locate

the

zero

around

the

resonant

frequency for the issue of stability.

2) Locate the pole around

Switching

for the noise

reduction at high frequency.

3) The combination of the above 2 procedures can

make the crossover frequency at the -20dB/

decade situation. Thus a satisfactory phase

AN021 Datasheet(PDF) 6 Page - Analog Intergrations Corporation

AN021 Datasheet(HTML) 6 Page - Analog Intergrations Corporation

Html Pages

1 2 3 4 5 6 7

Datasheet Download

Link URL