3 Phase PWM to drive 3 phase boost converter - Page 1
Forum section: electronics / projects

author: nmcgnyksl
author_rank: Newbie
timestamp: May 29, 2014, 05:00:21 pm
content: Hey guys, I'm new to the forum but i need your help on this stage of our boost converter.We are trying to generate 3 phase pwm signal to drive each mosfet and we are trying to do it via PIC. Could you tell me a dspic which we can generate these signals.Or if you can think of a new way please tell it to me it will be much appriciated.Thank you

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 29, 2014, 05:33:25 pm
content: Any dsPIC with the motor control PWM can do it. However, if you're running at a high frequency (more than 25kHz or so), you'll probably want to go with the newer ones that have better resolution.What input and output voltages and currents are you dealing with? A boost converter is good when the calculated duty cycle is around 50% or so. If it's much greater or lesser, some other topology probably would make more sense.

author: nmcgnyksl
author_rank: Newbie
timestamp: May 29, 2014, 05:37:07 pm
content: we will operate around 33% so a 3 phase boost converter will be a better option according to efficiency of boost. however this converter also will be a MPPT system therefore the resolution is much more important than the efficieny of converter.is there any other way like using logic gates that you can think of?our boost will be a 500W boost input is around 100V and output is aroud 150V

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 29, 2014, 07:47:21 pm
content: At that power level, just one phase is all you need. Even Toyota is only using a single phase boost for about 30kW.A low end dsPIC with the digital power PWM would probably be the best choice for your application if you want a "purely digital" approach. Or you can use a UC3525A (or similar) analog PWM controller with a low end PIC controlling it via a DAC. (The "DAC" can be as simple as a bunch of resistors!)

author: nmcgnyksl
author_rank: Newbie
timestamp: May 30, 2014, 09:14:46 am
content: thanks i will look up for efficiency of one phase boost converters. But making it three phase is like a fantasy.

author: jaxbird
author_rank: Frequent Contributor
timestamp: May 30, 2014, 01:44:29 pm
content: I did some experiments using a PIC to control a multiphase buck converter. I had to settle for 2 phases as that was all I could do with a PIC24 at 100kHz. You'd need something with individual timers (control the offsets) for 3 PWM outputs for that to work, I don't think that is common in PIC/dsPIC.Anyway, a link to my experiments:https://www.eevblog.com/forum/projects/multiphase-buck-converter-controlled-by-uc-with-cv-and-cc/I didn't really have a goal, but low ripple was something I was aiming for.I guess you could try a CPLD or FPGA to do as many phases as you'd like.

author: nmcgnyksl
author_rank: Newbie
timestamp: May 30, 2014, 05:03:24 pm
content: i thought about FPGA too but its is rather expensive and we need to built our own design to be able to join the solar car race. thanks btw i looked up to your project. it will give me some ideas

author: jaxbird
author_rank: Frequent Contributor
timestamp: May 30, 2014, 07:13:48 pm
content: Quote from: nmcgnyksl on May 30, 2014, 05:03:24 pmI think a ~$1 CPLD might do the PWM workload with multiple phases for you, but not sure whether it's worth the extra effort in efficiency.