Do you need a Deluxe Analogue Power Supply?

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chemelec

Well-Known Member
Here is a Supply that can handle almost Any amount of Voltage or Amperage. Just Choose the appropriate output Transistors.

**broken link removed**

Origionally based on an IC, but here I have designed it and built it with descrete components. (except for a comparator to give a I/E mode indicator, if wanted)

Gary
 
chemelec said:
Origionally based on an IC, but here I have designed it and built it with descrete components. (except for a comparator to give a I/E mode indicator, if wanted)
Click to expand...

My main comment is that it's rather over complicated!, simply because you appear to have recreated the original IC with discrete components, based on the original internal circuit of the IC?.

This isn't a very good way to design a circuit (as I'm sure you know?), IC internal design is often done in different ways because of the method of construction, and the difficulty in creating certain components.
 
Actually this design was done in conjunction with Direct Feedback from the Engineers at Motorola.

And Although Not quite as Perfect as the IC, It Does work very well.
And even though it looks complicated, The Actual cost to make this is Very Cheap.

Besides, trying to buy the MC1466L today will cost you in Excess of $100.00 US, if you can even get one.

Yes you can Design Simpler Supplies, But the MC1466L has Particular Features that have substantial advantages over those supplies.
 
Hi Chemelec,

On the power supply you have built, can you post the change in output voltage between no load and full load, as measured using a DVM connected to the output?

This is the one of the most important tests of a regulated power supply.
 
Just a Quick Test With the Voltage Set at 20.5 volts and No Load.

Measuring Directly at the Supply Output to Prevent Voltage Drops in the wire Leads.

Between no load amps and 4.1 amps out, the Voltage changes from 20.5 volts to 20.47 volts

This is the best I can do without making up a Special Resistor Load for the 8 amps. I don't have very many High Wattage Resistors.

Gary
 
Obviously Good Wiring is Important. And LARGE WIRES on the Output.
Definately a Stable Resistor for "RS".

I have 3 Foot, Very Flexable Leads coming off of my supply for Just General work and the Voltage drop across those leads at 4 amps is almost 1/2 Volt.

But for Most applications I don't need the Exact Voltage Control, Just running most IC and transistor Circuit.
And Most applications in running High Current, is just Motors or such stuff stuff where the exact Voltage isn't Critical.

But If Needed, I can get the Accuracy.

This Supply Isn't for Everyone, But it works for me.

My Power Supply Doesn't Incorporate the I/E Indicator. That was a after thought I thought would be Useful, but I never updated my unit.

Sometimes I get Lazy to do these additions on my own stuff.
Just Like Making things look Pretty. More important is it Works Relilably.

Pretty, Its NOT. That is why there Isn't a Picture of my Supply in the article.

Take care.........Gary
 
Regulation looks very good ! Aside from suitable wiring and available input power, how is the stability on large transients such as inductive inrush?

Reason for asking is that I am considering building a heavy duty supply to replace the one I am using now. Some of the ciruits I have involve alot of inrush ( 12 volt motors, lamps) and the control electronics don't perform if the supply rings or sags. I have local regulation, filtering, etc built into the devices that protects the control circuits suitably when installed on a vehicle with large batteries and heavy wire, but for testing I would like to get away from having to use batteries.
 
zevon8, Sorry I haven't actually tested it for that.

I have Run a lot of motors and no apparent problems.
Do you have a Specific Test setup for this that I could maybe Duplicate?

Gary
 
Hi, thanks for replying.

The load is 20 lamps, 18 Watts each, at 12.8 volts DC. The steady current is handled well by the supplies I have tried ( Amateur Radio mobile gear SMPS's ) the problem is the inrush current, which is 5 or more times the steady current.

During the inrush, the supplies will sag, then overshoot on rebound, and often ring. This plays havock with the electronics, causing random resets, and other nonsense. Generally making troubleshooting a nightmare.

What I use now is an industrial battery charger, rated 65 amps continuous, (the transformer is a 18 inch square monster ) with four 250 AH deep-cycle golf cart batteries for smoothing. Everything is connected by copper buss-bar and works well. All of this stuff was free scrap, hobbled together, so money for the regulation and power section would hopefully cost less than a comercial PSU capable of doing the job.

My biggest concern is the safety hazard of the batteries. I don't need a hydrogen explosion
 
Well you could make this supply to handle that kind of Current, But My supply is 8 amps at 36 Volts Max.

So my Current Limit won't allow me to test for your conditions.

I would "Assume" if you made it to handle 65 amps, It will hanle your motors quite well. And I Doubt there would be very much Overshoot if built properly.

But if you expect it to be Current Limited to 20 Amps, but Handle a 65 amp Surge on Motor Startup, It Won't.

You Can't have it Both Ways. Current Limit IS "Current Limit".

I will be away Till Wednesday, So any further questions will have to wait. I leave home, Early in the morning.

Take care........Gary
 
Thanks for the reply Gary, yes if I set a current limit it would defeat the purpose, but what I really want is voltage regulation to hold during large changes in current. I won't be limiting or regulating the current with the supply. Sorry I didn't explain it very well.

Ante, true PWM would work and the funny bit is, that is exactly what used to be done with my circuit. I had PWM at a low enough rate to do "keep warm" of the filiament just below visable levels. It extended lamp life and stopped the inrush current. However, it also increases the average draw on the batteries when installed on a vehicle, reducing the run time. It was also a bit of a delicate balancing act to get the right PWM rate for the lamps and not introduce noise and create problems for other electronics on the vehicle. Once I thought I had the perfect PWM rate but it caused the lamps to produce a very annoying "chirp" by vibration . Higher frequencies actually started to radiate electrical noise.

It is a bit of a poser, but so far straight on/off with a supply and wiring capable of the inrush seems the best solution.

Thanks for the help!
 
Substation transformer wanted

zevon8 said:
The load is 20 lamps, 18 Watts each, at 12.8 volts DC.
...the problem is the inrush current, which is 5 or more times the steady current.
Click to expand...
If the steady load is about 28A then you are suggesting that the inrush could be 140 A or more :?:
That's gonna be one juicy PSU.
 
Re: Substation transformer wanted

mechie said:
....If the steady load is about 28A then you are suggesting that the inrush could be 140 A or more :?:
That's gonna be one juicy PSU.
Click to expand...

LOL, it is, but the inrush is very short in duration. It is long enough though to create lots of noise on the power rails though. Heavy cable and vehicle batteries have no problem doing this, but creating a PSU to do the same is not easy.
 
Re: Substation transformer wanted

zevon8 said:
but creating a PSU to do the same is not easy.
Click to expand...
I can imagine :!:
The only way I can imagine a "sensible" PSU (around 30A :shock: ) coping with that is with a big, fat capacitor on the output ... ex mainframe computer PSU or car audio job (1 Farad?) ... can they cope with that kind of ripple current ?

Or you stick with that rack of lead-acid doorstops across the rails.
 
Hi zevon,

What I really meant was to use the PWM only at startup to eliminate the inrush, it would add a short delay but no waste of energy. 8)
 
ante: yes, that is the best method, however the same mechanical/electrical noise is produced, just for a shorter time, so I got a "ping" instead of a "chirp", if you know what I mean, LOL. What I did to produce the "soft-start" was have a gated PWM signal synced with a steady pulse, such that there was a short series of burst leading into a steady on pulse. This worked OK, other than the problem of noise.

The other solution tried was a microcontroller that generated a PWM that rose from barely on to full-on, then faded back again. This did work very well, however the microcontroller itself introduced alot of other "issues." Most of the problems related to the vehicles electrical noise upsetting the micro, since the device needs to be operating while the vehicle is restarted, unlike most vehicle electronics. The simpler design I now use with just inverter oscilators seems to be very tolerant of electrical noise, and if it does stop, it restarts without anyone noticing.

I realize most of the micro issues could be designed out, or programmed out, but sofar the KISS method prevails.
 
Hi zevon,

I would try a higher PWM frequency and avoid involving a micro (with its issues) as the base. As for starting the engine, the PWM must be disabled until the alternator starts charging i.e. while the charge indicator is on.
 
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