Unregulated power supplies and voltage regulators

[dxhound]

Ok, Im not much into keydowns and who can stomp who. But those of you who do, you might be able to answer my questions. The 150 amp + power supplies offered by Fatboy and xforce are unregulated and float at 18v. I also see coltage regulators listed on there site for Alternators. Is it possible (and easy) to use these regulators on the power supplies offered by them to knock em down to 14v?

 

[Justme]

You would need some hefty regulator for it, with an hefty heatsink.

The reason they donot regultate is simple, under heavy load the unregulated supply voltage will drop, thenn the resistance in the supply cables will lower the voltage even more to the transistors.

To keep the transistors fed with 14 - 15 volt, they use this less elegant method.

When building PSU's i always have an input for the voltage as measured IN the P.A. that measures thee voltage directly at the driven device(es).

That measurement voltage is then fed back to the PSU, wich will regulate the voltage up/down to keep the voltage at the set level at the devices.

Their methode circcumvents this, but you run the risk that the transistors might die from an overvoltage.
Most devices are specified at max 18 volts at the collector in respect to emitter.

Even feeeding the transistors with 15 volts you need to dish 150 amps at 3 volts, wich is 450 watts to dissipate.

For my 50 amp PSU i use to work the FT100 and FT847 i have an rather big heatsink with 8 x 2n3772 and the 60 amp full wave bridge rectifier on it, with an temperature controled 4" fan to cool it.

I can short the PSU at 50 amps and leave it for 24 hours without the PSU going bust, that is how i tested it.

At that moment i have to dissipate 50 amps at 17 volt unregulated in the heatsink = 800 watts......

At least it generates some heat, hence you need an big heatsink, and an good fan to dissipate the heat, large wiring, and good cooling.

I can set the max amps i want to limit the PSU, but it should handle the murphy factor, because it has 2 quite expensive transcievers connected to it.

One reason i buildt my own PSU's

Cor

 

[W5LZ]

The 'mainest' difference is 'where' the voltage regulation takes place (internal regulation of the power supply, an outboard regulator, or none at all). Using/not using a regulator depends on the device being supplied with power. Some devices are more tolerant of voltages excursions than others. Just depends on the particular components and circuits used to make that device.
Don't know about you, but I'm 'happier' with a regulated power supply than I am with an un-regulated supply. Just one more thing less to go wrong. Cheaper in the long run, sort of...
- 'Doc

 

[Cheech]

You cannot use the regulator form an alternator for a power supply. The alternator regulating circuit is diffrent from a power supply type regulator. If your looking for a big regulated power supplt check out the Iota RV power supplies. Price per amp they are the best bang for the buck and rated at 100% Duty Cycle.

 

[dudmuck]

Ok, Im not much into keydowns and who can stomp who. But those of you who do, you might be able to answer my questions. The 150 amp + power supplies offered by Fatboy and xforce are unregulated and float at 18v. I also see coltage regulators listed on there site for Alternators. Is it possible (and easy) to use these regulators on the power supplies offered by them to knock em down to 14v?

The question to ask is why you want to regulate it.
These fatboy/xforce power supplies are intended for class-C amplifiers.
Class C amplifiers are OK with 18 volts supply when there is no RF input, because the transistors are OFF without RF.
As the RF drive (and current draw) is increased, the voltage from the supply drops and the transistors are operating a lower comfortable voltage under load.
The voltage drops because there is some resistance in the bridge rectifiers and transformer windings. Its more important to have a hefty capacitor on the DC to absorb the AC hum.

A regulated power supply has whats called pass transistors which vary their resistance according to a controller chip intended to output a constant voltage regardless of current load.
These pass transistors dissipate lots of power and create heat which is an unnecessary waste for the common class C amplifier.

The alternative to such pass transistors is a switching power supply such as those used for the everyday desktop computer. However their low voltage output requires several units in series to get the right voltage. They are only cheap because of the ubiquitous volume production, but they are often noisy and require added ferrites.

 

[dxhound]

So what exactly is in those external voltage regulators? Do they take place of an alternators internal reg? I thought they were used as inline regulaors between the power source and the load.

 

[rlnthndr]

The question to ask is why you want to regulate it.
These fatboy/xforce power supplies are intended for class-C amplifiers.
Class C amplifiers are OK with 18 volts supply when there is no RF input, because the transistors are OFF without RF.
As the RF drive (and current draw) is increased, the voltage from the supply drops and the transistors are operating a lower comfortable voltage under load.
The voltage drops because there is some resistance in the bridge rectifiers and transformer windings. Its more important to have a hefty capacitor on the DC to absorb the AC hum.

A regulated power supply has whats called pass transistors which vary their resistance according to a controller chip intended to output a constant voltage regardless of current load.
These pass transistors dissipate lots of power and create heat which is an unnecessary waste for the common class C amplifier.

The alternative to such pass transistors is a switching power supply such as those used for the everyday desktop computer. However their low voltage output requires several units in series to get the right voltage. They are only cheap because of the ubiquitous volume production, but they are often noisy and require added ferrites.

Note you could also use scr's for regulation that operate similar to a SMPS but with out the noise and cleaner output.

 

[linearone]

unregulated power supplies are ok in tv sets, computer monitors, tube amps both rf and audio, all types of radios, some cb's, telephones, cell phone chargers.... but when it comes to the high tech, super high precision world of cb radio amplifiers... oooooh its better to be regulated... pfffttt.

 

[Captain Kilowatt]

Unregulated supplies are OK for something that draws a constant load but a very poor choice for something that has a dynamic, or varying, load. A radio used on AM would not be affected too much but when switched to SSB it would warble due to tye voltage dropping on voice peaks. It would also tend to fylat top as well. Same thing for an amp. On AM,not bad even with some flattopping but on SSB not good at al due to the flattopping and resulting distortion.

 

[Cheech]

So what exactly is in those external voltage regulators? Do they take place of an alternators internal reg? I thought they were used as inline regulaors between the power source and the load.

They limit the voltage to the inner coil in the alternator and that afects the voltage out coming from the outer coil.

 

[TonyV225]

I agree with you guys on these supplies and Unregulated I simply dont belive in exspecially when running on of my HF rigs or other Ham gear. Hell I wouldnt run a CB on a unregulated supply its simply scary just thinking about it. Im in no way or means cutting anyone builders supplies reliability or performance but regulated is more of a secure feeling not saying they also cant wig out Ive seen some serious damage done by regulaters popping and 30 + amps firing through a board in a radio and its not pretty looking, sounding or smelling. A nice supply like justme builds is the way to go and being to adjust that voltage is the cats @$$. I actually for my mobile HF amplifiers use an ETA supply they are not pretty looking (INDUSTRIAL COMERCIAL LOOKING) and theyare not pocket book friendly. My ETA supply is regulated at 13.8V 100% duty cycle at 88 AMPS and about $800.00 shipped Brand new I was going to get another one to link to this one I have but will probally buy 2 astron 70M instead for the price of another one of these ETA 88 AMP. The guys building these unregulated must be doing good however seeings how there selling so whos to say or throw any stones. Its just my personal preference to run regulated I have several supplies of different amperage and even like the Pyramids I have now some hate them and call them junk but Ive had great luck with them other than my 25 amp needed a bridge rectifier replaced but it was used when I got it so I replaced it with a bigger (50 volt unit) its a common problem in alot of supplies including the supplies in base radios and amplifiers the inrush current when turning them on will alot of times after alot of use sometimes sooner then later blows out the rectifiers. The inrush is the clunk pop or bong noise you hear when powering the unit up. Pyramid has what they call the (CROWBAR PROTECTION ) system which protects your equipment hooked to the supply unit from a over voltage burst due to regulator or simular power or voltage failure do to a misshap or faulty part. I would love to find a regulated 150 - 200 Amp power supply builder

 

[unit_399]

TonyV225 -

Actually, unregulated power supplies are more reliable. There are only three components: transformer, rectifier, and filter capacitor(s). The output voltage is determined by the transformer secondary voltage and the type of rectifier used. Either half or full-wave. For amatuer or cb equipment, an unregulated supply is fine as long as the unloaded to loaded voltage range is within the limits specified for the equipment. In mobile operation, the system voltage in a vehicle can vary from 12.4 to 14.8vdc depending on system load and engine rpm. Basically, these are the same conditions as in an unregulated power supply. So why is it "scary" to connect amatuer radios to an unregulated supply??? If the supply fails, the equipment is unaffected.
A regulated supply, with the excessive heat generated by the pass transistors, is much more prone to failure. And... unless the supply has overvoltage protection circuitry, if it does fail (usually a shorted pass transistor) full unregulated voltage (usually 25 volts or more for a 13.8 volt supply) will be applied to the equipment, and you can pretty much kiss it good-bye.
Unregulated supplies are easy to build. An old microwave transformer can be easily rewound to provide low voltage and high current. Use stud mounted diodes for the rectifier and a one farad aftermarket hi-power car stereo capacitor, and you're ready to go. Ripple voltage (noise) is minimized by the high value cap. I built a unit like this 10 years ago to power my 450 watt linear, and it's always worked perfectly.

- 399
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