Does boosting voltage on solar lower current ? - Page 1
Forum section: electronics / general

author: carpetpaul2129
author_rank: Contributor
timestamp: May 01, 2022, 08:30:24 am
content: As ever, I’m still in the early stages of learning and I’m a slow learner at that ! I was looking at a solar panel and the ability to use a boost converter to raise the voltage from the 21(ish) to 36v. When I read about these boost converters they sound like a miracle, but I’m guessing Ohms law must still apply, so if we raise the voltage, we automatically have a lower current ?…. How’re, would I be right in thinking that the total amount of power delivered / work that can be done is unchanged, just that we needed 36v to run our device ? And we’ve not lost out as such by boosting the voltage up (apart from minimal losses caused by the boost converter itself ?)Thanks

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 01, 2022, 09:14:23 am
content: Your supposition is correct however a boost converter is unlikely to make a suitable load for a solar panel by itself due to the characteristic of the solar panel (see attached data sheet). What load are you proposing on the 36V boost converter output ?Ooops, sorry no curves in Axitec, see QcellsThe problem with your boost converter is the lower the input voltage the more current it will try to draw (assuming a fixed load) and this will cause the PV voltage to further reduce resulting in voltage collapse. A PV panel needs a load that maintains it at or near Maximum Power Point, for example a converter regulating it's input voltage rather than it's output voltage.

author: Faringdon
author_rank: Super Contributor
timestamp: May 01, 2022, 10:47:20 am
content: Yes , thats right by fourtytwo42, you need a MPPT booster...one which regulates its output volts, but also clamps the input current of it to the value which gives MPPT....so its vout will droop as the load increases above that level which draws the mpp current.Analog.com have a lot of chips which will do this for you...eg LT7805 (?) , but theres more

author: Marco
author_rank: Super Contributor
timestamp: May 01, 2022, 06:04:14 pm
content: Quote from: carpetpaul2129 on May 01, 2022, 08:30:24 amYes, a boost converter has the same output power as input power, minus some losses.Maximum power point is only relevant if you have storage. If you have a PV panel and you simply need 36V with no significant storage (ie. more than a smoothing capacitor) you just boost. Either you get 36V at your desired load current, or you don't. That's as good as it's going to be.

author: james_s
author_rank: Super Contributor
timestamp: May 01, 2022, 06:06:57 pm
content: A boost (or buck) converter can be thought of in a simplified sense as a transformer that works on DC. You can exchange current for voltage or vise versa but you cannot get something for nothing, power out is always power in minus losses which are typically from a few up to about 20 percent.

author: carpetpaul2129
author_rank: Contributor
timestamp: May 02, 2022, 08:13:53 am
content: Thank you so much for the replies, interesting indeed. I have no specific application for this, but I’m working on simple projects at the moment, so just trying to get my head round some concepts. I could really do to find a course at a local college or similar

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2022, 04:54:30 pm
content: A simple analogy that works fairly well here is a gearbox. You can use gears to exchange speed for torque. If the output shaft spins faster than the input shaft it will deliver less torque and vise versa because the total power is the same, minus losses from friction.

author: Faringdon
author_rank: Super Contributor
timestamp: May 02, 2022, 06:38:23 pm
content: QuoteAttached is a Boost converter in the free LTspice simulator...from analog.comYoutube has some good vids on how to use LTspiceAlso, here is a free SMPS course, should you wish.....many LTspice sims within it...SMPS course_Big foldershttps://drive.google.com/file/d/17ij_pQLkAzzYeL_TRNci86sXHMirKHmD/view?usp=sharingSMPS course_little foldershttps://drive.google.com/file/d/1WvElhDNfHI0EBei4rouSNEdWWTO1oCtJ/view?usp=sharing