Buck/Boost,Cuk converter IC - Page 1
Forum section: electronics / projects

author: curiousmech
author_rank: Newbie
timestamp: August 27, 2014, 08:17:06 pm
content: Greetings,I need to design buck/boost or CUK converter to charge a battery.Input= 16V 7AmpOutput= 11~14V 5 AmpI need to know if their are any IC's AVAILABLE which can control the output via pwm from controller.

author: electros6
author_rank: Regular Contributor
timestamp: August 28, 2014, 02:28:50 am
content: what is the need for a buck_boost controller when the output voltage is less than the input voltage . There is lot of controller available in the market. Search for your suitable in digikey like sites.

author: curiousmech
author_rank: Newbie
timestamp: August 28, 2014, 01:30:43 pm
content: the basic idea is to charge the 12V 45Ah lead acid battery at constant voltage i.e.,14V irrespective of the varying input between 10~16V at a max current of 5Amp which is approx 10% of total current

author: David Hess
author_rank: Super Contributor
timestamp: August 28, 2014, 07:16:41 pm
content: There are lots of ICs which can do that but I think all of them will require an external power switch. 5 amps is pretty high for a SEPIC converter but possible I think.http://www.linear.com/product/LT1619http://www.linear.com/product/LTC1624A push-pull converter with a transformer might be better at that current level.

author: curiousmech
author_rank: Newbie
timestamp: August 28, 2014, 08:06:02 pm
content: well i don't see any sort of pin available to vary the buck/boost the voltages by varying dutycycle of the pwm

author: David Hess
author_rank: Super Contributor
timestamp: August 28, 2014, 08:45:29 pm
content: Quote from: curiousmech on August 28, 2014, 08:06:02 pmAny PWM controller can do this by having a current injected into the feedback node. The controller automatically adjusts the duty cycle to meet the requirements for keeping the feedback node at the same level as the reference. In this way you can control the output voltage with an external signal.

author: curiousmech
author_rank: Newbie
timestamp: August 30, 2014, 06:31:01 pm
content: i made buck using lm2678 and it worked but i have to make a Res network to provide volt to FB pin, when i directly applied pwm via ucontoller the behavior was not up to the mark, the res network prove to be best...so it depicts it can't be controlled via pwm

author: Mr Carlsons Lab
author_rank: Newbie
timestamp: August 30, 2014, 10:41:16 pm
content: The tried and true TL494 will do the job. Just go to data sheet archives and get the data sheet. They even have something like your trying to do as an application note. (Fairchild datasheet) Just mod some values and away you go.

author: kiran_shrestha
author_rank: Regular Contributor
timestamp: August 31, 2014, 04:35:21 pm
content: You can try MC34063 IC ,its really cheap and you can also add current limiting feature in it. Here's one of the example of the circuit with external switch.http://shortedwire.blogspot.com/2014/08/buck-regulator-design-10.html

author: curiousmech
author_rank: Newbie
timestamp: August 31, 2014, 05:53:19 pm
content: Quote from: kiran_shrestha on August 31, 2014, 04:35:21 pmactually i want to control the output voltage by pwm, so is it possible that "fb" pin can be fed pwm(average voltage)by ucontroller to make it control and avoid the Resistor network