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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 10th Mar 2023, 7:40 pm   #1
G6Tanuki
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Default High Power 3 [and 4] terminal voltage regulators.

In the late-70s/early-80s there were a bunch of rather-beefy low-voltage regulators - both fixed- and adjustable.

Nice easy-to-work-with TO-3 cases, and handling up-to-5-Amps.

LM117K/LM317K "Steel", LM150K were the 3-terminal variable versions; Fairchild had the 78H12KC 3-amp fixed 12V regulator and for variable-voltages at up to 6 Amps peak/5 Amps continuous they had the 78HGKC.

Again, TO-3 cased, so easy to heatsink. I used a bunch of such regulators in various designs - but they were marked-down as 'obsolescent' in the 90s.

These days you can't get high-current linear regulators; they've all gone TO-220 which makes 'serious' heatsinking a pain.

I guess SMPS have driven them out of existence.
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Old 10th Mar 2023, 10:39 pm   #2
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Default Re: High Power 3 [and 4] terminal voltage regulators.

You can still use "Steel" bypass transistors to increase the current capability of lower power regulators.
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Old 13th Mar 2023, 5:54 pm   #3
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Default Re: High Power 3 [and 4] terminal voltage regulators.

I do have some NOS 3A and 5A TO3 regulators if anyone needs one. They always go down well at radio club junk and swap nights!
-Jeremy
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Old 13th Mar 2023, 6:33 pm   #4
cmjones01
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Default Re: High Power 3 [and 4] terminal voltage regulators.

Yes, nobody will design a high-power linear regulator in to a product any more. In fact, for any current greater than about 50mA, I'd go straight for a switching regulator. Negative rails are a bit more difficult, but inverting boost converters are perfectly practical. A design I did a couple of years ago contains various power rails (a variable one for relay coil economising, +16V and -15V for some op-amps) and they're all derived from a +12V power supply using software in a microcontroller which also does a lot of other jobs. The only "analogue" components involved are switching MOSFETs, inductors, capacitors, perhaps a gate driver, and feedback resistors. The rest is just software, which means that the power supplies can be remotely monitored and controlled if required.

More and more power supplies are done this way.

Chris
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Old 14th Mar 2023, 8:04 pm   #5
G6Tanuki
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Default Re: High Power 3 [and 4] terminal voltage regulators.

I've done the "wrap a series-pass-transistor-or-three-around-a-1A-regulator" thing in the past, but it introduces a load of extra components [and soldered-joints] each of which bring footprint, cost and reliability issues, apart from the hassle of trying to balance the current across several 'helper' transistors while stopping the whole thing achieving its ambition to become an oscillator at some particular transient combination of load-current and reflected load-impedance.

Pragmatically, the linear-regulator is a dead thing, SMPS having beaten it into the ground.

Sad, and annoying.
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Old 14th Mar 2023, 8:44 pm   #6
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Default Re: High Power 3 [and 4] terminal voltage regulators.

Quote:
Originally Posted by G6Tanuki View Post
Pragmatically, the linear-regulator is a dead thing, SMPS having beaten it into the ground.

Sad, and annoying.
A board I have next to me here contains a regulator which will cheerfully deliver three or four amps at 5V from a 12V input. It takes up less PCB space than my little fingernail, is cheap, and doesn't get hot.

Apart from the vastly reduced size, weight, component cost and assembly cost and enormous gains in efficiency and reliability, what have the switching regulators ever done for us?

Chris
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Old 14th Mar 2023, 9:08 pm   #7
kellys_eye
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Default Re: High Power 3 [and 4] terminal voltage regulators.

Switching regulators?

A lot of noise over nothing......
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Old 14th Mar 2023, 9:15 pm   #8
radioman
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Default Re: High Power 3 [and 4] terminal voltage regulators.

You can still get 5A adjustable regulators like this one (in a TO220 package) :-https://uk.farnell.com/stmicroelectr...220/dp/1087148

Andy
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