dc/dc converter for VRLA battery charger

We decided to design the vrla battery charger for ups application. we have chosen four stage method for battery charger. Noe our en-quire is,we need to charge the battery at constant current mode if the battery voltage is below some level and also we need to charge the same at constant voltage level if the current level is reached ( basic four stage)

how to achieve constant current at one time and constant voltage mode at one time period in hardware or converter.... ie,by using microcontroller we can control the converter,but how the converter changes the mode,because we can control only PWM signal through microcontroller. not the mode.. is it?

which topology is better for this difffernt modes.. dc input === 250-400Vdc charger output = 12-204Vdc ,charger current= 5-20A.....


need your valid suggestion...

i have a doubt on charger output voltage, you want to charge a single battery or battery bank, it is not possible huge variation in output voltage.
In any type of charger SMPS/Buck converter it will have two feedbacks current limit and voltage limit, if battery is deep dicharged battery draws constant current i.e desined current limit and if battery reaches sufficient level current decreases and constant voltage will be maintained.

murali_dece said:

i have a doubt on charger output voltage, you want to charge a single battery or battery bank, it is not possible huge variation in output voltage.
In any type of charger SMPS/Buck converter it will have two feedbacks current limit and voltage limit, if battery is deep dicharged battery draws constant current i.e desined current limit and if battery reaches sufficient level current decreases and constant voltage will be maintained.

Click to expand...

Actually what i meant is, suppose if we need charge the 12v battery system means the battery charger systems should support for that and also if we want to charge the 204V (17*12=204) means,the charger should support..ie.,universal charger. and also for different Ah level..

Then regarding CC and CV mode,we have to design separate duty cycle limit for current control and for voltage control... in-case of current control the current limit duty cycle control will control the pwm signal and in-case of voltage,corresponding voltage loop duty cycle will work..

is it?