Higher voltage power supply - Page 1
Forum section: electronics / beginners

author: KOR
author_rank: Newbie
timestamp: November 07, 2021, 06:59:48 pm
content: Hi,is it possible/easy to design a powersupply which basically uses a bridge rectifyer directly followed by a buck converter to get output voltages between 200 and 60 V. (240VAC Mains). In my ideal world the PWM and sensing for the buck converter is done by a teensy and the output power is at least 200W.In my newbe electronic mind that should not be a huge problem but I guess there are several reasons why there are basically no buck converter in that voltage range.

author: Manul
author_rank: Super Contributor
timestamp: November 07, 2021, 07:56:44 pm
content: Can be done, but one issue is that the ouput will not be isolated from mains. Likely you don't want your buck output and everything connected to it to be riding mains voltage. Not to mention, that it is plain dangerous to play with such circuit without experience. There are also issues with efficiency, buck topology will likely not be a good choice for high voltage input or high ratio convertion.

author: KOR
author_rank: Newbie
timestamp: November 08, 2021, 10:01:05 am
content: Is there an alternative to achive the result 200W+ adjustable power supply with a range of 60-200V?Perhaps by adding a 1-1 Transformer to achieve the isolation?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 08, 2021, 10:45:20 am
content: The reason you do not see these often is because there is not much electronics that need such a voltage at that power level.How about this approach:You start with a 12V power supply, and then use the transformer from a PC power supply in reverse. So you put you amplified PWM into the 12V winding and you generate your 60V to 200V on what used to be the primary winding.This has the added advantage that all your driver electronics works with 12V low voltage, and is therefore easy to work with relatively safely.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 08, 2021, 11:35:30 am
content: You can use a 1:1 isolating transformer capable of supplying full power and then some. If you can afford that then you might as well go linear.In an smps, the isolation is provided by the converters transformer, feedback optoisolator and possibly an isolated gate driver too. So you need something like an isolated SEPIC. It can be boost or buck. You may find this useful. I got this usinghttps://www.poweresim.comR23 R24 and R25 set the ouput voltage. There are compensation components around this feedback, they may need some small adjustments. You could also pot down the volatge flowng in to the FB pin but its on the mains side so carries more risk.Remember that lethal voltages are present and a cap the wrong way round may explode. Take full precautions.How much ouput current do you want and what adjustment range do you need?

author: KOR
author_rank: Newbie
timestamp: November 08, 2021, 06:14:37 pm
content: I like to have a range between 200V and 60V as output voltage. at 200Vdc I like to be able to draw 1-1.5A at 60 3-4A should still be possible.Ideally my powersupply would use a couple pins of my teensy 4.1 to regulate the output voltage.

author: Jwillis
author_rank: Super Contributor
timestamp: November 10, 2021, 07:22:32 pm
content: Quote from: KOR on November 08, 2021, 06:14:37 pmI'm not an electronics engineer by any respect but here's an idea that may help .Have a look at theLR8high voltage regulator . With appropriate current pass transistors you could achieve your current requirements . Your Teensy could then be used for voltage adjustment through a digital potentiometer and monitoring current and voltage . You would need some galvanic isolation between the high voltage and your Micro controller . That could be done with opto-isolators .The biggest issue would be the current pass transistors would need to be able to dissipate at least 200W . Shouldn't be to hard for 1 to 2 amps .