Adjustable HV PSU

[Beardyman]

Morning all,

I saw these online & decided to get a couple, they were less than a fiver each. It's obviously an SMPS which I don't usually play with in connection with valved equipment as usually there is far too much RFI/EM from them. Anyway, the optimistic specs say it'll take 10-32VDC in & give 50-400VDC out at up to 200mA. Hmm, I thought, we shall see. After some bench testing with various loads it was obvious that if you push this to the upper limits it'll need a fan to cool it! It also needed some extra de-coupling when connected to my home brew hybrid amplifier, another 47uF to get a quiet output for 250V @ 100mA. Input voltage is about 22VDC & its pulling about 1.5A. Regulation isn't bad, from zero to 100mA there is perhaps 5V difference. As an alternative to an HT transformer it worked for me. I did have to fit an earthed screen over it to prevent it interfering with the pre-amp stage as it is physically close.

[turretslug]

Interesting!- and it would be churlish to pick too many holes in it at that price. Is it basically a power oscillator with step-up, as often found in 'scope HV circuits, or is the plastic power device an IC with greater circuit sophistication? A bit more civilised and rather more efficient than a dynamotor- and dynamotors are usually strapped to a comprehensive in/out filter pack anyway.

[g4aaw pete]

Sound like a couple of these could be used in a valve tester?

[Beardyman]

Its a bit more than that, I forgot to post a pic of the underside. They are available in dual output too so, theoretically you could get +/- 450VDC!?!

[turretslug]

Aha, thanks- you do get sophistication for the money then. That is impressive.

[trobbins]

That is the YH11068A module - schematic is on-line. It has been available for at least 4 years now. It uses a UC3843A controller, so it isn't ZVS.

Output voltage control includes pulse skipping and burst mode, so be mindful that it may move between modes for large load changes. If you were to populate the negative rail then note that it is not regulated. Heatsink is floating, and like any switchmode, the FET dissipation and cooling needs to be appreciated and managed appropriately.

I use it in a valve tester jig, as the module can be run from a 12V battery and so doesn't need a mains AC connection and so minimises hum loops, which helps to keep measurement spectrum plots 'clean'.

[turretslug]

I'm continually surprised at what comes out the great industrial power-house of China in torrents and for very little money. The Luddite in me would have liked it to be the simple power-oscillator mentioned, or even better a push-pull Royer, (got an LF one of these anyway) both of which are regulable to a degree, but I suppose this offers pretty tight output regulation and wide input flexibility.

It struck me that, if the claim of 200mA output was true, that this would make an easy route to powering a "universal"/"AC/DC" radio from a car battery (dropper on 200V tapping for efficiency, plus suitable filtering)- should anyone want to do such a thing!

[trobbins]

There are also a small number of neat buck (step-down) converter modules to provide eg. a regulated 6.3VDC if needed from a 12VDC supply. There are also step-up modules for generating bias voltage for audio amplifier output stages (including this thread's module) although it helps if either the B+ or the bias module has an isolated output.

Another useful module, with isolated secondary, comes in a few guises as a 150W inverter with 12VDC input and 120 or 240VAC output - the output can be on-board rectified and filtered to generate a few B+ levels (not continuously adjustable, and not regulated, so circa 120, 300 or 440VDC), and is based on a 3525A controller. It is identifiable by having a transformer and two FETs for push-pull primary. I've used this module in a 6CM5 PP UL amp, to provide both the 340V B+ and the -55V negative bias using different secondary winding sections.

[petervk2mlg]

Beardyman, can you post a link to the source of the items?

[Beardyman]

I'm not sure that is within the forum rules?
If you type YH11068A into the auction site search box that should get you where you need to be.
I was surprised the delivery time was only 10 days. I don't remember seeing any UK suppliers.

Hope that helps in some small way for you.

[barretter]

I don't think YH11068A will find them but "DC-DC boost converter" will throw up a lot of entries you can search among. Even if they say "London" as location I think they will still come from China.

[petervk2mlg]

Thanks. I found some like the attached

[AdrianH]

I have two of these with the negative rails and there is also one for use in valve pre-amps that has the buck converter on board for heater voltage.

Good if not pushed to far, or add bigger heat-sinks.

Adrian