Duty cycle range in DC/DC converter

[batistuta]

hi, all
in dc/dc converter, such as boost, usually have input voltage from 2.7v to 4.2v, and the output is 5v, so the duty cycle can calculate, one is 0.46(2.7v) the other is 0.16(4.2v), does it means this boost can work normal with 0.16<=D<=0.46?
now i have question:
1. which part confirm the duty cycle range? the error opamp output range?
2. now if i have input voltage is 2v, i also want the output voltage is 5v, how to do?

thanks.
batistuta

 

[batistuta]

Re: duty cycle range.??

i think the output is clamp by the divider resistor, so if the system is stable, the output will not change, but i want to know which feature change, when input out of the default range... efficiency ?or..?
thanks

 

[darla1]

Re: duty cycle range.??

hi can you tell me how you are generating pulse to boost, by pwm ic or any micro,

if it is by any pwm ic the error volatge will compare the refernce, and compensation also plays role..

 

[batistuta]

duty cycle range.??

not use pwm ic, i design it by producing a sawtooth wave and then compare with the output of error opamp and get the pwm signal,

1. i want to know, if input is from 5v to 12v and output is 3v, but if my input is 4v, and i also want to get the output 3v, does just the compensation network play the role??

 

[~E3016~]

Re: duty cycle range.??

what did you mean with the usually input value for boost? we can use any value for input if we design it ourself

can you be more specific about the boost converter, for example, what it's name code, specification ? from your question i guess that the boost have feedback control so it can run normally in the range 0.16 - 0.46 of duty cycle.