Hello, I would like to ask some informations about step converters.
I would need to control the output voltage digitally with PWM, on a boost converter.
I don't know practically if it is better to use an IC or a PMOS.
For example this is the schematic of an IC I found that may meet my needs for voltage and current:
If the VIN is coming from a LI-ION battery 3.7V, and the PWM is connected to EN pin, am I able to control digitally with Duty Cycle the final output voltage?
Or maybe do you recommend to use a PMOS schematic like this one? Where I connect the external PWM source to the Gate.
Extremely unlikely. You might be able to find a boost converter chip with a control voltage input, in which case a DAC would be used to produce the control voltage.
I don't know much about these things but usually the reference is DC (which could be filtered PWM or a DAC) and the switching regulator has its own PWM/switching controlled by a feedback loop to hold the output constant.
Yes this is what I am struggling with.
I have a 3.7v battery, and I would like to boost the output voltage from 4 to 12v and control it digitally. The load will be maximum 500mA.
The PMOS schematic you show is a generic schematic of a boost converter.
The PCB layout is just as important as using the correct components.
If you have never designed a switch mode power supply before, be prepared to go through many design iterations before you get it right.
Maybe, I would have to see the schematics of most step-up converter modules and the data sheets for all the ICs and then give me a few weeks to read everything.
You might want to start with these design tools.
Power Stage Designer and WEBench Power Designer
It is one of the solutions I had in mind before, but DAC can give me a better resolution in bits, so if I want for example a step of 0,1 volts for increasing and decreasing, I think I can do it well with a DAC feeding the FB pin.
What do you think of the schematic? Do you know how can I get the right resistances values?
You could decouple R1 from the output and instead connect it to a DAC. But then you'd still include the DAC and whatever controls it in the feedback loop of the DC-DC converter. That's a recipe for disaster.
The digital pot approach is the most logical one IMO. If the resolution of an 8-bit pot is insufficient, gang two of them together; one for coarse and one for fine adjustments. Or use a high/low range that you can switch between using something like a single CMOS switch that you use to include an additional resistor into the network.
What I would like to do is to change the output voltage, with a DAC voltage feeded to the FB pin.
According to datasheets of the IC's this is possible. All you did is just saying it won't work without saying your reasons, and without allowing me to understand why.
Yes of course, I get as gold all the informations you guys gave me. I explored the power designer which gave me a lot of solutions, but all static.
Since I needed a dynamic solution which I can control digitally, I then focused on the idea of the DAC that previous user gave me.
Again all the informations I get from all of your answers I try to study the application.
In the cases of replies like "No it will not work", without explaining why, to me are useless.
