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Common High Frequency Power Supplies

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LAN_403

quicksilver

Thu Jan 21 2010, 07:23PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

In a discussion at one time i was told that 12 v halogen lights (garden lights) use a high frequency PS. Not having the money to buy one and actually check- I thought about what would use a high frequency PS (non-50/60Hz). It would seem that small reading lamps that use florescent lights may but aside from custom applications there are not too many high frequency power supplies (it seems to me)

I went to an older electronic store that sells some very interesting old things and saw some test equipment that appeared to alter frequency with minor PS range. Looked to be vintage 1960's.
My question is; are there such things as common use high frequency power supplies in common use or is this quite unique high end engineering material rarely seen by the hobbyist?

MinorityCarrier

Thu Jan 21 2010, 07:58PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

The driving force behind what you refer to as "high frequency P.S." is efficiency. Back in the '60's most DC regulated power supplies were series-pass linear supplies with efficiencies of 40-60%. What you are calling high frequency, are either pulse-width-modulated (PWM) or switch-mode DC supplies, which have efficiencies of 80-95%. As a group these are called switching-regulated supplies. It's more economic to use these as they waste much less power.

You can buy switching supplies rated to run your halogen lamps online. They are quite common, but a bit more expensive than a series-pass supply. I wouldn't recommend buying a surplus electronics linear power supply unless you are comfortable with repairing it (it may not work) and you have power to burn.

Dr. Dark Current

Thu Jan 21 2010, 08:34PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

MinorityCarrier wrote ...

What you are calling high frequency, are either pulse-width-modulated (PWM) or switch-mode DC supplies, which have efficiencies of 80-95%. As a group these are called switching-regulated supplies. It's more economic to use these as they waste much less power.

I think the whole group of power supplies which use solid state switches and high frequency are called switchmode power supplies, and majority of these use PWM as a mean of regulating the output power in the control/feedback loop. There may be other means of controlling the output power (maybe FM in power supplies with resonant filters? Don't know) but I have only seen SMPS's with PWM.

MinorityCarrier

Thu Jan 21 2010, 08:55PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

My lazy. I'm referring to pulse interval modulation when I mistakenly said switchmode.

Steve Conner

Fri Jan 22 2010, 10:34AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The last two halogen lights I bought had HF power supplies. A set of kitchen counter lights from Ikea, and a table lamp from John Lewis.

Energy saving lamps have a similar circuit, just with a ballast inductor in place of the output transformer.

...

Fri Jan 22 2010, 09:40PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Almost any modern power supply can be modified to have such an output, for example people have used computer power supplies to power flybacks (by tapping directly from the main transformer, not by using it to power an external driver). Generally the cheaper the power supply the better, since they generally are simpler and have less circuitry that might need to be defeated to allow them to be hacked up to drive a new transformer.

IntraWinding

Fri Jan 22 2010, 11:32PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

The sort used to power halogen lamps were an early readily available example, but now most power supplies that connect to the mains are switch mode (high frequency). I tried to find an analogue supply recently of the type with all the works in an oversized plug for a very low noise circuit I built but discovered they're getting hard to find! This has happened without my noticing because the oversized plugs still look similar on the outside as when they had big iron transformers inside.

radiotech

Tue Jan 26 2010, 09:05AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Not modernly relevant but.. Part of my work used to be repairing 16 mm film projectors. The exiter lamp ran on high frequency from a single tube, 6V6 i think. They needed a quiet lamp, filtering DC too hard i imagine then. Also I have worked on old phonograph by Philco with hf lamp in pickup, mirror tied to needle. I went to the files and got the power supply manual for the Beckman DU spectro and it uses a high frequency smps Tube type. Weighs 54 lbs, consumes 540 watts, and runs 3 types of lamps, tungsten, hydrogen, or mercury as well as some photo cell/multiplier electronics. This ps is a replacement for the original. Everything used to a car size storage battery and a collection of dy cells and batteries. I wondered in another thread if anyone else has any DU's stashed. My chem prof said they were popular for the telesope crowd but that was in 1974.!

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