FP6329ASOGTR datasheet(12/16 Pages) FITIPOWER

12 / 16 page

FP6329/A/B-1.0-APR-2010

FP6329/A

85T

fitipower integrated technology lnc.

Application Information (Continued)

Compensation the Converter

The

FP6329/A

single-phase

converter

voltage-mode controller.

The design consideration

for a voltage-mode controller requires external

compensation.

Proper compensation of the system

will allow for a calculable bandwidth.

In most case,

a Type Ⅲ compensation network is recommended.

The target of the compensation network is to provide

the closed loop transfer function with 0dB crossing

frequency and sufficient phase margin (greater than

45°).

The buck converter is composed of three basic

blocks as Figure24 shown: modulator, output filter,

and

compensation

network.

Figure26

the

voltage-mode

control

loop

with

Type

Ⅲ

compensation

for

synchronous

rectified

buck

converter.

Modulator

Output

Filter

Compensation

Netw ork

Output

Reference

Figure24. Basic structure of the buck converte

Figure25. Voltage-mode buck converter compensation

The error amplifier output is compared with the

oscillator triangle wave to provide a PWM wave.

The gain of modulator is input voltage divided by the

ramp amplitude.

OSC

MODULAT OR

GAIN



OSC

MODULATOR

log

)

(

GAIN



The output filter includes the inductor and the output

capacitance.

Remember that do not ignore the

DCR of the inductor and the ESR of output

capacitor.

The transfer function for the output filter

shows a double pole break frequency at FLC of LC

filter and a zero at FESR of Co and ESR.

FILTER

)

DCR

ESR

(

ESR

GAIN



















Output filter break frequency equation







ESR







The open loop small-signal transfer function is

dominated by a DC gain and developed by the

double pole at FLC and a zero at FESR. Figure26

represents the Bode plot of the open loop system

gain.

The system has different double pole and

zero frequency.

The phase will decline a sharp

slope at the double pole for system with very low

DCR and ESR parameters.

System will more

difficult to compensate while the phase needs an

extra boost to provide required phase margin for

stability.

OSC

FILT ER

MODULAT OR

OPENLOOP

)

DCR

ESR

(

ESR

GAIN





















FP6329ASOGTR Datasheet(PDF) 12 Page - Fitipower Integrated Technology Inc.

FP6329ASOGTR Datasheet(HTML) 12 Page - Fitipower Integrated Technology Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL