Constant-on time control mode buck!!!

[smartdream]

constant on time buck

Can any one post some papers/links about constant-on time control mode of buck converter, it is urgent for me, very very thanks in advance!

 

[smartdream]

can anybody help? plzzzzzzzzzzz.....

 

[VVV]

I could not find much about it. Try searching the website of National and ON Semi.
Here is a part from National that uses constant-on-time **broken link removed**

Essentially, constant on-time does a good job when the input voltage range is large. In a buck the duty-cycle varies with the ratio of the output voltage to the input voltage. For high ratios, the duty-cycle becomes very small and the swithc has barely if any time to turn on. With constant-on-time you force it to be on a reasonable amount of time, to ensure complete turn-on of the switch. Then you adjust the frequency to keep the loop in regulation.

I hope this helps.

 

[smartdream]

I could not find much about it. Try searching the website of National and ON Semi.
Here is a part from National that uses constant-on-time **broken link removed**

Essentially, constant on-time does a good job when the input voltage range is large. In a buck the duty-cycle varies with the ratio of the output voltage to the input voltage. For high ratios, the duty-cycle becomes very small and the swithc has barely if any time to turn on. With constant-on-time you force it to be on a reasonable amount of time, to ensure complete turn-on of the switch. Then you adjust the frequency to keep the loop in regulation.

I hope this helps.

Hey guy, very thanks for your kindly help, and the "helped me" has sent to you! and can you show me its operating theory? can any one throw me some bright light on it?

 

[ynhe]

You can refer this document for simple theory and seek some Chip application notes and datasheet using Google,like LM1770 LM3100.

For the large input voltage range,You could change the Constant-on time according to the input voltage adaptively and keep the switching frequency pseudo-constant.

 

[smartdream]

thank you all!
any other description or materials?