Need Components equivalent for General purpose power supply circuit - Page 1
Forum section: electronics / beginners

author: audio
author_rank: Regular Contributor
timestamp: February 14, 2021, 03:45:37 am
content: Dear all,,This Circuit has been published 1974, today it is required to construct lab power supply. I need equivalent for this circuit with out compromising for the functionality. for example LM308 could be replaced by TL084 but no replacement for LM395. so request all to give equivalent for this circuit and thank all for spending your time as well ideas.

author: bob91343
author_rank: Super Contributor
timestamp: February 14, 2021, 04:17:12 am
content: I don't think that's such a good design. The voltage reference isn't all that great, and the 'current limited pass transistor' is a gimmick. There wouldn't be anything currently available to do that function as far as I know. And seven in parallel? Nope, find a more modern, more clever circuit.

author: bdunham7
author_rank: Super Contributor
timestamp: February 14, 2021, 04:48:26 am
content: I don't think the circuit is that bad. D1 is an inherently low tempco part and it looks like the current through it should be fairly constant. The LM395 is an interesting way to scale the design, but it works and eliminates emitter resistors or other methods of balancing the driver currents. All of the parts appear to be readily available except perhaps the LM308, which is widely counterfeited because the originals allegedly give guitar distortion pedals some unique sound. There are many pin-compatible replacements and even the fakes will likely work just fine in this circuit. It probably could be done more cheaply and with less heat, but that would be a different design.

author: audio
author_rank: Regular Contributor
timestamp: February 14, 2021, 02:38:53 pm
content: Dear all,This RPS will be used as test equipment and to construct Audio Amplifier in Future, so it should have lower ripple .In my cupboard i have 24v @ 10 ampere center tap transformer, after rectification it could give 24 root 2 which is 34V dc and Maximum of 5 ampere DC Current can be taken with out loading Transformer. The above NI Circuit was appropriate but the Component where obsolete. So I went on searching on NET and got IC power supply but MC1466L was again obsolete. Adjustable voltage regulate will not be beneficial when Input-output difference were higher, the current output will be smaller.For more than 3 decades LM723 Was used for deigning RPS. I went on designing with external power transistor with emitter resistor,heat sink but could not current limiting function in to action with foldback current limiting. So coming to NI Circuit has two loop one for voltage and other for current. when current exceed certain limit current loop will take in charge and lower the voltage and save all the series elements... this is what i have understood from the scratch for Building CC/CV Power supply.Could any body Suggest linear power supply whose output is variable up to 24V and power output is 100Watts(nearly 5 AMPS). It should be operate in CC/CV mode as well.Thanks in advance for Sharing your Knowledge and Time...Now any one in this forum could suggest me to proceed in proper direction.

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2021, 04:19:33 am
content: It is a fantastic design and higher performance than most with its low output capacitance providing above standard constant current response. Any deficiencies in the reference can be solved with a better reference.An LM301A should be used instead of the LM101A but there are no obvious modern alternatives to the LM301A because its compensation pin is being used for clamping to provide faster current limiting. An LT1008 *might* be made to work with some changes but it is hardly a better choice due to pricing and availability. I would keep the LM301A unless I redesigned the current limit for the LT1008 or some other part.The LM308 as used could be replaced with any number of alternatives, including the modern LT1008, LT1012, or LT1097 which are modern high precision equivalents. An OP-07 would be the inexpensive modern precision replacement. I have used the LT1007 in the past for lower noise but it requires careful consideration of external frequency compensation because of its speed in a circuit like this.The integrated output transistors are a big problem. They can still be had, but are very expensive, and without them, there is no built in protection. I have designed and built similar variable power supplies using common LM317 type regulators for the output pass elements to gain their built in protection and that could work here but some design tuning would be required.

author: bdunham7
author_rank: Super Contributor
timestamp: February 15, 2021, 05:16:27 am
content: Quote from: David Hess on February 15, 2021, 04:19:33 amJust curious why you would recommend that? It looks like the power supply spec might be exceeded for the LM301A (+/- 18V) where the LM101A and LM201A are (+/- 22V) .

author: audio
author_rank: Regular Contributor
timestamp: February 15, 2021, 05:38:33 am
content: Sir,Can you share the circuit with lm317..

author: srb1954
author_rank: Super Contributor
timestamp: February 15, 2021, 05:58:21 am
content: Quote from: bob91343 on February 14, 2021, 04:17:12 amI would've said that the voltage reference is actually pretty good, comparable or better stability than many monolithic regulators. If enhanced temperature stability is required it can be easily upgraded to a higher grade diode e.g. 1N829 which will give stability comparable to the very best laboratory PSUs.I don't know why you regard the current limited pass transistor as a "gimmick" as it is a effective way of protecting the output transistors against overloads. The adjustable main current limit circuit should perform quite well too given a stable enough current sense resistor although the response time might be slower than a simpler current limit circuit.Having said that this is a complex and expensive way to build a general purpose bench PSU. This circuit only makes sense where you really need to eliminate the large output capacitor present on most conventional PSUs

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2021, 12:30:34 pm
content: Quote from: bdunham7 on February 15, 2021, 05:16:27 amThe LM101A and LM201A are not as readily available but that is why they used them. An LM301A can be selected for 44 volt operation and the negative supply voltage to it can be reduced.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 15, 2021, 01:30:10 pm
content: I assume its the low offset and drift that matter in this circuit.There are not to many 44V op-amps around. The TLE2141 is not madly expensive. TL35072P cheaper still.See LT1001, LT6010, LT1007, LT1636, LT1637, LT1115, LT1494, LT1490... and alsohttps://www.onsemi.com/products/amplifiers-comparators/operational-amplifiers-op-amps#products=fjI1MDIyNzF+dmFsdWV+MX40NC4wfg==

author: bdunham7
author_rank: Super Contributor
timestamp: February 15, 2021, 03:35:42 pm
content: Quote from: audio on February 15, 2021, 05:38:33 amWhat David is describing is a fairly unusual and complex way of using the LM317 as an output pass element. I'll let him elaborate, but if you truly need a power supply with no output capacitance (fast response), excellent constant current operation and adjustability all the way to zero volts, the design you have is pretty good and the parts are not obsolete--at least not here in the US. If you have trouble getting those parts, let us know and we might come up with substitutes. If I were making a precision bench supply, I would certainly consider this design that you have posted, although I might use a different voltage reference like an LM399.If your purpose is to use this power supply for an audio amplifier, you may not need to be able to adjust all the way to zero and you may not need constant current operation, just overcurrent protection. In that case, a much simpler adjustable power supply would do quite well. I'll link one example, read it and see what you think. You can use an LM338 regulator with a large heat sink and you won't even need extra transistors.https://www.bristolwatch.com/ele/lm317.htm

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2021, 05:11:46 pm
content: Quote from: Terry Bites on February 15, 2021, 01:30:10 pmFor the current control loop, the LM301A has an input range which includes its positive rail and it has a compensation pin which can be used for clamping.For the voltage control loop, offset and drift may be why they selected the LM308 although it is only better than average.

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2021, 05:23:54 pm
content: Quote from: audio on February 15, 2021, 05:38:33 amThere is not much to share. An operational amplifier is used to drive the adjustment pin so the LM317, or other integrated regulator, is enclosed within the operational amplifier's feedback loop and contributes no errors of its own. The complication is that the LM317 has its own frequency compensation so some attention may need to be paid to the compensation of the operational amplifier, but this is not too difficult and slow operational amplifiers which are suitable for a general purpose power supply like the LM308, LM301A, 324, 741, etc. require no special consideration. The LM317 essentially replaces an NPN power transistor configured as an emitter follower and any driver transistors with the input being the collector, the base being the adjustment pin, and the emitter being the output.Note that this works just as well with higher voltage integrated regulators although their quiescent current usually flows through their common pin instead of output so they should be buffered as shown below. I usually replace the JFET configured as a source follower with a bipolar PNP emitter follower. The buffer transistor is not required with an LM317 because its adjustment pin current is microamps but might be included anyway with a 120 ohm resistor between the output and adjustment pin to provide the minimum load current.

author: audio
author_rank: Regular Contributor
timestamp: February 15, 2021, 05:54:02 pm
content: Could any body share the other linear power circuit to design. We will see the other perspective and move on further..

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: February 15, 2021, 11:14:48 pm
content: An analog-drivable Protected MOSFET is made by some manufacturers which could probably be substituted for the LM395s at a lower cost and you could probably use fewer then the seven shown in the schematic. Example:OmniFETseries from STmicroelectronicsVNP5N07Edit: If you use fewer then the seven transistors, then thermal considerations would become important to watch if it were to be used at high power.

author: audio
author_rank: Regular Contributor
timestamp: February 16, 2021, 03:11:38 am
content: Would this circuit will be good?

author: srb1954
author_rank: Super Contributor
timestamp: February 16, 2021, 07:23:13 pm
content: Quote from: audio on February 16, 2021, 03:11:38 amNo. The 2N3055 transistor will likely die the first time you short the output.The current limit circuit is dubious as well. The emitter of the current limit transistor (pin 3) can be pulled below the IC substrate voltage (pin 7) when sufficient transient short-circuit current flows. This could cause the 723 to behave unpredictably due to stray internal currents through the inherent substrate diodes in the IC.

author: David Hess
author_rank: Super Contributor
timestamp: February 16, 2021, 09:59:11 pm
content: Quote from: Infrared_Fred on February 15, 2021, 11:14:48 pmAre those suitable for linear operation? The datasheet only mentions protection in switching applications.

author: audio
author_rank: Regular Contributor
timestamp: February 18, 2021, 12:32:09 am
content: Is there any other solution to this specifications?

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: February 18, 2021, 02:33:35 pm
content: Quote from: David Hess on February 16, 2021, 09:59:11 pmAccording to the first page of the datasheet, the circuit has direct electrical connection to the MOSFET's gate during normal operation so it can be used for analog driving, albiet the datasheet seems to indicate it is a fairly slow device. Another similiar product which does specify directly switching or linear appliucations is theBTS117and other HITFET® Infineon Techology series MOSFETs.

author: audio
author_rank: Regular Contributor
timestamp: February 19, 2021, 02:17:49 am
content: How it is better to go with Lm723 ic? So we will proceed the construction with 723 ic. It is better the circuit with 723 ic which can operate in cc cv mode...

author: xavier60
author_rank: Super Contributor
timestamp: February 19, 2021, 02:27:52 am
content: There is some discussion about CC mode with the LM723,https://www.eevblog.com/forum/beginners/bench-top-power-supply-from-the-past-opinions-and-some-help/msg3418316/#msg3418316

author: David Hess
author_rank: Super Contributor
timestamp: February 19, 2021, 10:05:51 pm
content: Quote from: Infrared_Fred on February 18, 2021, 02:33:35 pmI saw that, but the protection circuits may not operate properly at low gate voltage.

author: audio
author_rank: Regular Contributor
timestamp: February 20, 2021, 04:11:14 am
content: Hi all,,Please suggest me alternative circuit for my specification.Thank you all..

author: xavier60
author_rank: Super Contributor
timestamp: February 20, 2021, 04:28:50 am
content: Quote from: audio on February 20, 2021, 04:11:14 amThis is a thread I linked earlier then pulled it. I'm not certain of your skill level, I'd rather see you attempt this design than other designs out there.https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg3345000/#msg3345000Ill add links to variants of this design that other members have successfully built as I find them.Do you understand opamps?https://www.eevblog.com/forum/projects/how-this-linear-psu-circuit-works-and-why-it-doesnt/

author: audio
author_rank: Regular Contributor
timestamp: February 20, 2021, 04:49:47 am
content: I am a undergraduate student who is interested in design and development but money and availability of components is problem here.Thank you sir for your threads. Xavier sir can you recommend rps specification and circuit.. Thank you...

author: xavier60
author_rank: Super Contributor
timestamp: February 20, 2021, 05:11:09 am
content: The PSU that I actually built uses a transformer with two 15VAC 3A secondary windings that are configured as parallel or series to suit the output voltage. I allow it to supply up to 5A on the low voltage range and 2.5A on the high voltage range as it is fan cooled. It has two TIP35C BJTs on a large fan cooled heat sink.I don't see any ripple with my DSO in CV mode, a little ripple in CC mode.https://www.eevblog.com/forum/projects/linear-lab-power-supply/msg2388873/#msg2388873The last few pages of the threads that I linked have some useful information.

author: audio
author_rank: Regular Contributor
timestamp: February 20, 2021, 11:37:42 am
content: Thank you all.....

author: xavier60
author_rank: Super Contributor
timestamp: February 20, 2021, 11:42:54 am
content: If you build this design, let us know when you are ready to test it.

author: audio
author_rank: Regular Contributor
timestamp: February 20, 2021, 12:38:53 pm
content: Definitely sir.. Thanks a lot...

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: February 23, 2021, 03:13:14 pm
content: Ia am interested in building the (originally mentioned in this thread) power supply design, but I don't need or want the 10A capabilty (too much power to worry about). To scale the current back to say about 5 amps or so, could I change the 0.1resistor to 0.2or 0.22and posibly reduce to 4 LM395s in parallel rather than 7? Any other mods nessacery for this?Thanks!P.S. Sorry if this seems rude, but I wouldpleaselike the question awnsered, rather than just something like "look for a different power supply design". Again, Thanks!

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2021, 05:05:04 pm
content: Quote from: Infrared_Fred on February 23, 2021, 03:13:14 pmYes, this is a reference design and it is provided so that you can understand it and then modify it. Increasing the sense resistor is one way, but try to understand what each part of the circuit does and you'll see that there is more than one way to accomplish what you want. Also keep in mind that this circuit will dissipate quite a bit of heat, especially with a high current at a low output voltage. Also, you need to provide the unregulated but filtered V+, the V- and you have to be mindful of the absolute maximums for the op-amp power supplies. A transformer supply that yields 30VDC under full load might give you 42VDC no-load, and that's too much.

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: February 23, 2021, 06:51:15 pm
content: In regards to the power supply, I was thinking thatthisone orthisone andthisone together. Both of the 36V power supplies specify that they can be adjusted down to ~32-33V so I would probably use that option to save on unnecessary power dissipation, and/or I may add a capacitance multiplier to reduce switching noise on the power supply which would drop a volt or two.Thanks!

author: bdunham7
author_rank: Super Contributor
timestamp: February 23, 2021, 10:22:32 pm
content: Quote from: Infrared_Fred on February 23, 2021, 06:51:15 pmThat's an interesting way to do it--is it cheaper than a regular transformer? The first one looks ideal--the isolated 5V part can be connected for the -5V part.

author: Infrared_Fred
author_rank: Regular Contributor
timestamp: February 23, 2021, 11:40:58 pm
content: Quote from: bdunham7 on February 23, 2021, 10:22:32 pmBased on the ~$70 of the capacitors + transformers + rectifiers of the transformer "source" power supply vs the $~78 of the switching power supply + capacitance multiplier + cooling fan (see .xslx attached Digikey carts for both), I think I would rather go with the SMPS since the price is only really different by $3-4 for the capacitance multiplier since the fan would be necessary on the chassis anyway even for the linear and the SMPS is going to be lighter and *probably* more efficient.

author: audio
author_rank: Regular Contributor
timestamp: February 28, 2021, 06:45:37 am
content: Which mode of operation is better ? In case of Cost and complexity?Switch mode power Supply or Linear mode power Supply...You all can give working Circuit using Switching Regulators for my specification(30V @ 5 amps).My application is Designing Amplifier for Audio frequency and Charge my Battery which is used in Inverter(12V 10 amps)