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#11 |
diyAudio Member
Join Date: Sep 2020
Location: SiChuan
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Google Translate seems to be unable to fully express my thoughts, haha. I plan to get a voltage of ±60V from the main power supply of the power amplifier because I don't want to add new windings to the transformer. While maintaining good performance, it needs to be reduced to ±15V in the simplest way. At least 200ma current is used to drive 5-6 operational amplifiers. It has a huge heat sink, so it can get good heat dissipation support, and I don't care about power consumption. Based on this requirement, I first thought of lm317/lm337 because it can provide good enough performance and is simple enough, but its maximum withstand voltage cannot meet the requirements. I thought of using two lm317s in series to solve the power consumption and withstand voltage problems, and considered using TVS to protect the lm317 from accidental damage. I don't know whether the whole circuit is strong enough after using TVS, or whether the operational amplifier will be damaged by accidental ultra-high voltage. If this idea is feasible, can lm337 do the same? This is my initial thought.
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#12 | |
diyAudio Member
Join Date: Sep 2020
Location: SiChuan
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Quote:
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#13 | |
diyAudio Member
Join Date: Sep 2020
Location: SiChuan
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Quote:
thank you! |
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#14 |
diyAudio Member
Join Date: Mar 2011
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I had this trouble of a too high voltage for a LM317.
My solution was using a TL431 ( a shunt regulator ) and a BJT to deal with the high voltage. In this solution, the BJT emitter is at the regulated output, the collector at the unregulated voltage. The TL431 has the anode at ground, the cathode at the BJT base, its ref input senses the regulated output voltage with an appropriate voltage divider. For an improved low ripple, I use a CCS to feed de BJT base and give at least 1mA to the TL431. This solution is my favorite and is fine for up to 35V positive regulated PSUs. Very flexible using Skyzlar pair for high current.
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Transistor junction temperature is not transistor case temperature. |
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#15 |
diyAudio Member
Join Date: Mar 2011
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Can one dream simpler ?
1 Pass BJT. 1 Shunt regulator: TL431. 1 Output cap ( about 100uF ) 1 Resistor divider: 2 resistors. 1 CCS: 2 cheap BJT + 2 Resistors. For +15V -15 V. Make two positive regulators, feed them from two independent secondary windings with 2 diode bridges. Connect outputs so to have your central ground. This is far better than the usual center tap winding, followed by pos and neg complementary stuff that only advantage is purely cosmetic.
__________________
Transistor junction temperature is not transistor case temperature. |
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#16 |
diyAudio Member
Join Date: Sep 2003
Location: Liège
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This might not be possible if you are getting your +/-60v from an existing supply...
edit: btw, if this is for opamps, with decent psrr to start with, one might not need a lm317/337 pair at all. A pair of big bjt (one pnp, one npn), two 15v zeners, two resistors and two output caps are all that's needed if ample dissipation is available. Not efficient though.
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All that is excessive is insignificant. Talleyrand Last edited by 00940; 4th December 2020 at 09:14 PM. |
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#17 |
diyAudio Member
Join Date: Dec 2015
Location: south east asia
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Use LM5001. It is 75v can be used as step down positive voltage, but here is a circuit for negative.step down.JPG
It will always be noisy, this why it needs to follow by a linear regulator. Last edited by kokoriantz; 5th December 2020 at 12:15 AM. |
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#18 |
diyAudio Member
Join Date: Sep 2020
Location: SiChuan
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Thank you all friends upstairs, I have got several feasible solutions from your replies.
As part of satisfying my curiosity, I tried a simulation. The simulation looks okay. Maybe I can try to make one. LM337 Tracking Preregulator Circuit |
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#19 |
diyAudio Member
Join Date: Jan 2003
Location: mississauga ontario canada
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Don't forget to simulate the first turn-on of the supply.
Use a step or pulse function for the 60V. Look at all voltages and currents for all devices.
__________________
Doug We are all learning...we can all help "You can't stop the signal, Mal. Everything goes somewhere..." |
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#20 |
diyAudio Member
Join Date: Mar 2009
Location: Buenos Aires - Argentina
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00940 is quite on the spot.
No need for a tour de force using inadequate LM317 and praying they share voltage equally which will NOT fail safe under any problems, use parts which can each stand 60V rails (and more, play it safe), period. Solution is robust and cheap: 1) use TIP31C-32C with 2k2 2W resistors Collector to Base and 20-22V 1W Zeners Base to Ground as preregulators. You´ll get 19-21V DC You may add small 10uF electrolytics from emitter to ground 2) use LM7815-7915 as final regulators, following datasheet suggestions. That´s it. Forget the dangerous idea of clamping diodes as you mentioned, they will either "do nothing" or explode. Simulate it if you wish, not really necessary, I have been doing this thousands of times for decades, in abused Guitar amps and powered mixers. No need for quirky switchdown preregulators or anything else, everything off the shelf stuff.
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Design/make/service musical stuff in Buenos Aires, Argentina, since 1969. |
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