What's inside of these modern electronic ballasts

[tangerine3]

What's inside of these modern electronic ballasts for florescent shop lights and other straight tube fixtures? I know these ballasts are being sold more and more to replace the old iron core magnetic types, but what's going on inside of them? Obviously there are semiconductors and other electronic components. I would suspect that a capacitor discharges to start the bulbs.

I tried to google a schematic, found several showing how to wire them (same as the old style ballasts), but none show the innards or a schematic that explains how they work.

I also wonder how durable and reliable they are compared to the old ones? Electronics are often more likely to burn out from power line surges caused by lightning and load surges. Since surges occur in all electrical systems, are the electronic types as durable as the old coil wrapped around iron ("transformer") types.

Thanks

[gregz]

You got bridge to make dc, mosfets to switch at high frequency, inductor and caps. More efficient but probably less reliable, but ballasts break too.

Greg

[Bob_Villa]

From the ones I have installed...they are at least as reliable. The 4 ft-4 tube ones are 125-270volt. So they must clamp the voltage. The lasts ones I received were even smaller now. Although as long, maybe slightly bigger than an inch square.

[Tomsic]

The circuitry is fairly basic: RF filter, surge protection, ac-dc power supply, inverter (dc to high-frequency ac), current limiter (fluorescent ballasts are constant-current devices) and starting circuitry.

The surge protection feature has been included since the 1980s when the first electronic ballasts were used in buildings. Whole buildings were converted, lightning struck and whole buildings went dark with ballast failures. One manufacturer went bankrupt trying to honor warranty replacements. Doesn't take too many of those to get the attention of the industry.

No, the new electronic ballasts don't appear to be as durable as the old "core-and-coil" types -- not much to go wrong with a wire wrapped around a few steel plates; but just like a TV or any other electronic device, the circuitry is reliable depending upon the manufacturer. A bonus is that lamps are more efficient and last longer on electronic ballasts. I built a house 10 years ago with indirect fluorescent lighting in most of the rooms. There are 20+ ballasts. So far, one lamp has failed -- no ballast failures. And, last year set a new record for rain and lightning storms in the area.

Just like any other electronic device, I think heat and capacitor wear out are or will be the cause of most electronic ballast failures. CFL bulbs are good examples of that.

Tomsic

[Jim Yanik]

gregz wrote in news:1216010132358050972.266977zekor- [e-mail]:

I took apart a cheapo dollar store 60W CFL(spiral type),and the ballast was a 2 transistor circuit with a tiny ferrite core transformer and a couple of electrolytic caps configured as a voltage doubler,that rectified and doubled the input line voltage. this was all in a space the size of a new dollar coin.

The input V is rectified and doubled to around 300-320 VDC,then the transistors switch the DCV through the transformer to generate the higher AC voltage to power the FL tube. The tube filaments are in series across the transformer output and are energized at cold start by the high impedance across the tube until the arc discharge begins.the arc effectively shorts out the filaments,so they don't burn up during normal operation.

I doubt that throwaway CFLs will have any surge protection.

I suspect that the wear items for an electronic ballast will be the electrolytic caps,as they are in other power supplies and electronic circuits.

[Peter]

Nothing like good old planned obsolescence. How much would it really cost the manufacturers to substitute electrolytic caps with somewhat higher power ratings? I'd gladly pay an additional $0.20 - $0.50 per CFL or fixture for substantially longer mean time before failure.

[Tony Miklos]

As long as electronic ballasts are lasting (fairly long in my opinion) I'd bet they are already using a high quality cap where it really counts... on the high frequency circuits. Electrolytic caps often suffer from ESR, and the only place this is normally a problem is the high freq switching circuits and if they where using cheap caps there, the life of a ballast may be only a year or two. I'm having much better luck with el cheapo "lights of america" brand ones. No complaints here.

[Jim Yanik]

Peter wrote in news:jo8un4$pul$ [e-mail]:

the caps in there are 105degF 250V caps,seem to be rated fine. electrolytics DO have a finite lifetime,usually several thousand hours of operation. But the CFLs often are in "hot" environments that shorten their lifetime. That's why many are not rated for "base up" operation;the ballast receives the heat from the fixture.

switcher power supplies usually put a fast rise waveform across the caps,that have high harmonics and generates a lot of internal heat. electrolytics lasted a lot longer at 60Hz frequencies and sine-wave operation.

[tangerine3]

Is this bad capacitor thing "planned obsolescence"? It must be. That's all I hear in the last decade. Computers, and other electronics, ballasts, and the list goes on.......

Back in the 1960's and 70's I worked on electronics as a hobby and did repairs. Much of the stuff was old vacuum tube stuff and early transistor stuff. I *rarely* had to replace caps. It was normally a tube, transistor, bad connection, or a bad potentiometer. When a cap went bad, the device did nto stop working, just there would be hum in the speaker from a weak filter cap. Much of the stuff I worked on was

20 or 30 years old. In fact I still have a 1940's tube type shortwave radio and it still has the original caps and works well.

You'd think that with our technology that caps would be BETTER than they used to be..... instead they're junk. If they want to keep putting these foreign made junk caps in our electronics, maybe everyone should stop buying the crap until they begin using good caps. I'm sure they can make good ones......

[clare]

MOST are now better than they were 10 years ago. There was a batch of counterfeit electrolyte out there from guess where - it starts with ch and ends in a.

Capacitors from even the best manufacturers ended up affected.

That crap has worked its way out of the system -more or less.

No telling what is in some of the cheap crap coming out of there today

- but at least now the problem is known.

[Stormin Mormon]

I'm open to ideas. Is the poor quality a plan to get us to buy more items, as they don't last as long?

How much cap would a crap cap cap, if a good cap could crap cap?

Peter Piper picked a peck of pickled Picofarads.

Six thick sticks, twixt six thick thumbs?

Christopher A. Young Learn more about Jesus

.

[Tony Miklos]

Yes old technology was easy on caps, especially a simple filter cap from a big old analog power supply. Today's tiny switching power supplies push caps to their limit. Sure they could use different style caps, maybe mylar would last longer, at about 50 times the price and 100 times the size.

[tangerine3]

That sort of explains my point about the old electronics still working. Particularly when the old vacuum tube stuff produced a lot more heat around the caps. I could be wrong, but as far as I know, all those old caps were made in the USA. Sprague, and Mallory come to mind as the top brand names from that era. Maybe if America started making electronics including the components, we would once again have reliable equipment. That old stuff was made to last, but these days is made to generate a fast dollar and create lots of pollution during the discard and trash phase. Whatever happened to "American pride". There is not one fully made in America electronic item made these days and I hear it's the same with cars. Even American made cars have parts made all over the world.

[John Gilmer]

Regardless of how good you make the electronics, the fluorescent tube gradually loses efficiency. The plasma inside the tube will cause parts of the electrodes to "sputter" off. At the minimum this will damage the phosphor. There is a "getter" effect whereby the sputtered metal can trap some of the Hg.

Just like in the old Model T Fords, good design is to make all the parts so that they reach economic end of life at about the same time.

Within the last 2 or 3 years, the CFLs have become MUCH better. I have them all through the house and I might replace ONE CFL each month. Replacement just isn't much of an issue anymore. I use two as "night lights" where they burn 24/7.

That said, the LEDs are gradually coming into their own. Some of the earlier consumer LED had a very short life but most seem OK today. One lamp "fogged up" because, I suspect, a poor choice of plastics in the construction.

White LEDs are actually fluorescent devices with a UV LED causing the phosphor to glow. My understanding is that the phosphors are slowly damaged by the UV light and lose efficiency. Almost all LEDs still use resister ballast.

When & if "they" throw electronics into LED lamps, the electronics would have to be an order of magnitude more reliable than that used for CFLs simply because the LED itself lasts at least an order of magnitude longer that an Hg based fluorescent tube.

[clare]

Cheap crap uses resistors - good stuff uses constant current source IC devices

The single chip LED drivers are VERY reliable. And quite cheap too.

[Ashton Crusher]

Several years back I noticed that the tubes in my newer 48" fixtures were burning out fairly fast, like within a year or two. Googling for info at the time (at least 5 years ago now) I found that the life expectancy for the tubes when used in electronic ballasted fixtures was less then half the expected life when used in magnetic ballasted fixtures. I replaced those "new" fixtures with mag ballasted new ones and started getting my usual 3 to 5 years of life again. I also noticed that in our commercial building all the ballast for the fixtures continues to be mag ballast, not the electronic crap.

[Tomsic]

Your data may be correct, but the conclusion is not. Fluorescent lamps experience the longest life possible on electronic ballasts -- and, yes, it's just certain ballasts. That's because optimized electronic ballasts start the fluorescent lamps with a "starting scenario" where the proper voltages and currents are applied in just the right way as the lamps start. Fluorescent lamp life is highly dependent on the way lamps are started.

It's not uncommon these days for fluorescent lamps in commercial service on optimized ballasts to last 40,000 - 50,000 hours.

Lighting fixtures, ballasts and lamps for home use have been "detuned" so that lamp and ballast life may very well be short. That was done in the name of energy savings, but there's no excuse for it since it increases costs for home owners and makes the product less sustainable. The solution, however, is simple. Buy your lamps and ballasts from electrical distributors (like Grainger and others who sell on line) and use commercial rated products. Stay away from the junk sold as "residential".

Electromagnetically-ballasted fluorescent systems are about 30% less efficient than electronically-ballasted systems. You may get longer lamp life, but you are paying for more energy to get it.

Tomsic