PWM-FF vs PWM-QR control IC

[Mauri]

Hi all,
i need to understand when is better to use a PWM-FF (fixed
frequency)IC's instead of a PWM-QR (quasi resonant)IC's or viceversa,
in a smps design.Which are advantage and disadvantage, of the two
solutions ? Following the link i'm looking at

http://www.infineon.com/cgi/ecrm.dll/ecrm/scripts/prod_cat.jsp?oid=-8178

thanks

mauri

 

[Mauri]

Hi all,
can somebody help me ?

thanks in advance

 

[legg]

Hi all,
i need to understand when is better to use a PWM-FF (fixed
frequency)IC's instead of a PWM-QR (quasi resonant)IC's or viceversa,
in a smps design.Which are advantage and disadvantage, of the two
solutions ? Following the link i'm looking at

http://www.infineon.com/cgi/ecrm.dll/ecrm/scripts/prod_cat.jsp?oid=-8178

Anytime that system EMI or other reasons for employing synchronization
are critical, a variable switching frequency will present problems in
application and cost.

Most of the advantages of QR switching are just as easily obtainable
at fixed switching frequencies, without involving the primary
resonance of the main energy storage or safety isolation elements.

RL