Having shocked myself so many times now on mains level electronics, I'm literally getting uncomfortable watching you handle the circuit. I'm not a nanny, I know you know what you are doing, it is my problem not yours. But man, I kept saying "noooo" in my head. Really enjoyed the series, I've learned quite a bit from all your videos and have been subscribed for a long time. Please keep it up!
Interesting, I was just building something extremely similar!! Keep in mind that the LM317 has a minimum load current. This is a little different for the different versions. I think the "M" version has the lowest. 5mA or so, the other ones go up to 8mA. I would recommend using a full wave bridge rectifier to bring down the noise even more at the output. They are so cheap these days.
Hello P_Mouse! Well, I did address the minimum load current, but in the LM317L TexasInstruments datasheet its only 1.5mA Typ. I guess its different for different manufacturers. Regarding the rectifier, I only used a basic diode to keep things simple and to illustrate the filtering capability, but you are right, for a proper circuit implementation, diode bridges will be needed. On other hand, with a single input AC winding, to get a differential supply, you will still need this single diode scheme..
@@FesZElectronics Yes, it can really differ. I used them also for some cathode (self) biasing and got all kinds of strange behavior. Changed to another one and it worked just find. Looking back to the datasheet, I was just in the "danger" zone. Around 5mA or so if I recall. I am planning to make some HV buck converter in front. Basically just to get rid of all the heat dissipation. I am planning around 400Vdc output and 150mA, with a 150V minimum or so. So on the lowest voltage setting that means the circuit is dissipating around 37,5W. Maybe I can also just use a double winding and switch in between, although that can give some nasty spikes sometimes.
Building a power supply with a SMPS pre-regulator stage and Linear post regulator stage is quite common. Its the best way to get the best of both worlds. I guess you can keep the LM317 and set the feedback of the SMPS to follow the output of the LM regulator; so basically replace the capacitance multiplier in this schematic with the SMPS.
@@FesZElectronics Yeah, that is basically my idea. Although getting a flyback stable is the tricky part. I was also thinking of not making a tracking regulator, but just set the voltage (very) roughly 10-15V higher or so. It doesn't have to be precise. The capacitance multiplier can still be useful, since it's a actually a lot better of getting rid of high frequency noise. The noise reduction of a LM317 isn't actually so great for these higher frequencies.
Looking forward to Part 2b! It is my understanding that it's not difficult to implement an overcurrent protection by using a 0.1-1 Ohm shunt resistor and a comparator or an op-amp. To make it work as it's done in modern power supplies (drop the voltage but keep the current constant) may be another story.
Hello Alex. I tried to make the circuit as simple as possible, that is why I refrained from adding op-amps. But since a dedicated current limit does seem to be necessary, I think a single transistor one will suffice...
Thanks for the great videos. I have 3 questions: 1 - What are the values of the common capacitors (C11, C12, C14) in the schematic ? 2 - Have you tried to make a direct short circuit on the output to GND and did the power supply survive this? 3 - Can I have 2 transformer windings and use 2 bridged rectifier and connect the 2 GND (+ and -) from them together in the same circuit ? Best Regards Peter
Hello Peter! Let's take things one by one: 1 - I used 10nF but any value will do 10-100nF; 2 - I slowly increased the current, but Idid not do a direct short circuit; I expect the result to be the same at the moment - no survival... 3 - This will work only if the 2 initial windings are separated; so its common to have transformers with a large winding and an intermediate pin (3 pins total) - this will not work; but if the windings are separate, then its ok; Regardless you can try and simulate this circuit in LTspice and confirm there is no issue, the windings can be voltage sources to keep things simple
@@FesZElectronics I have previously built a variable high voltage power supply (50-400 V, 200 mA), for my experiments with tubes, not with an LM317, but with an FET and a transistor as a current limiter. In it I had to build a thyristor and a relay to deal with a direct short circuit. Good idea to use LTSpice to test with 2 bridged rectifiers, I will do that. Thanks, Peter
Booooy, I see what you are trying to do. Are you trying to do HDC voltages for pedal tube valves? Because, if yes... damn man, I was trying a solution for that. I mean, a small circuit, small noise, high voltage dc to excited the tubes (12ax7). Great work as usual.
Well, that was not the plan, but its a good idea! I will keep this in mind. What sort of pedals are usually built with valves? distortion or also something else?
@@FesZElectronics Hiho. Well, I'm yet a rookie working with guitar fx. As far as I am concerned we can build distortions, some audio amplifiers and sustain and compressor pedals (but compressor ones are too fancy ~to do not say complicated~)
I do not understand why you feel the need to match temperatures on the FET and regulator? done that with say totempole arrangements where you want each to have the same point on the transfer curve, but not different devices.?
@@FesZElectronics Not on part 2b yet, but looking at the reference sheet, can see some omissions, like the 2.2R resistor on the output filter to limit inrush current, plus you seem to have a capacitor where it tells you specifically not to insert one, I will be very surprised if you ever get this regulating, even on part2b, we shall see, I tend not to diverge from reference designs much unless they can be calculated accurately, the guys at national will be using the best simulators and engineers to take all parameters into account, including thermal limits. When we used to do simulations, we swept lots of parameters, monty-carlo, worst case-tolerence etc, bit of a pain, but on HV circuits like this, its probably wise.
Well, I'm not building it for a particular purpose, but its a high voltage linear supply, that can be used anywhere you need clean stabilized high voltage - one example can be in vacuum tube circuits.
This circuit is just about precisely what I've been looking for, and your explanation is excellent. Many thanks!
Glad it was helpful! May I ask what are you building?
Having shocked myself so many times now on mains level electronics, I'm literally getting uncomfortable watching you handle the circuit.
I'm not a nanny, I know you know what you are doing, it is my problem not yours.
But man, I kept saying "noooo" in my head.
Really enjoyed the series, I've learned quite a bit from all your videos and have been subscribed for a long time.
Please keep it up!
I always learn something from your videos, keep up the great work!
I can see simple and good electronic design. Thanks!
Thanks! It was informative.
LoL.....I was waiting to see the fire extinguisher in action ; )
Btw. The max working voltage of resistors also has a lot to do with the creepage/clearance distance.
Very good analysis
Great series!
Interesting, I was just building something extremely similar!!
Keep in mind that the LM317 has a minimum load current.
This is a little different for the different versions. I think the "M" version has the lowest. 5mA or so, the other ones go up to 8mA.
I would recommend using a full wave bridge rectifier to bring down the noise even more at the output. They are so cheap these days.
Hello P_Mouse! Well, I did address the minimum load current, but in the LM317L TexasInstruments datasheet its only 1.5mA Typ. I guess its different for different manufacturers. Regarding the rectifier, I only used a basic diode to keep things simple and to illustrate the filtering capability, but you are right, for a proper circuit implementation, diode bridges will be needed. On other hand, with a single input AC winding, to get a differential supply, you will still need this single diode scheme..
@@FesZElectronics Yes, it can really differ.
I used them also for some cathode (self) biasing and got all kinds of strange behavior.
Changed to another one and it worked just find.
Looking back to the datasheet, I was just in the "danger" zone. Around 5mA or so if I recall.
I am planning to make some HV buck converter in front. Basically just to get rid of all the heat dissipation.
I am planning around 400Vdc output and 150mA, with a 150V minimum or so.
So on the lowest voltage setting that means the circuit is dissipating around 37,5W.
Maybe I can also just use a double winding and switch in between, although that can give some nasty spikes sometimes.
Building a power supply with a SMPS pre-regulator stage and Linear post regulator stage is quite common. Its the best way to get the best of both worlds. I guess you can keep the LM317 and set the feedback of the SMPS to follow the output of the LM regulator; so basically replace the capacitance multiplier in this schematic with the SMPS.
@@FesZElectronics Yeah, that is basically my idea. Although getting a flyback stable is the tricky part.
I was also thinking of not making a tracking regulator, but just set the voltage (very) roughly 10-15V higher or so. It doesn't have to be precise.
The capacitance multiplier can still be useful, since it's a actually a lot better of getting rid of high frequency noise.
The noise reduction of a LM317 isn't actually so great for these higher frequencies.
Excellent!
Looking forward to Part 2b! It is my understanding that it's not difficult to implement an overcurrent protection by using a 0.1-1 Ohm shunt resistor and a comparator or an op-amp. To make it work as it's done in modern power supplies (drop the voltage but keep the current constant) may be another story.
Hello Alex. I tried to make the circuit as simple as possible, that is why I refrained from adding op-amps. But since a dedicated current limit does seem to be necessary, I think a single transistor one will suffice...
@N01Spl it is
Awesome channel, subscribed.
Thanks for the great videos. I have 3 questions:
1 - What are the values of the common capacitors (C11, C12, C14) in the schematic ?
2 - Have you tried to make a direct short circuit on the output to GND and did the power supply survive this?
3 - Can I have 2 transformer windings and use 2 bridged rectifier and connect the 2 GND (+ and -) from them together in the same circuit ?
Best Regards
Peter
Hello Peter! Let's take things one by one:
1 - I used 10nF but any value will do 10-100nF;
2 - I slowly increased the current, but Idid not do a direct short circuit; I expect the result to be the same at the moment - no survival...
3 - This will work only if the 2 initial windings are separated; so its common to have transformers with a large winding and an intermediate pin (3 pins total) - this will not work; but if the windings are separate, then its ok; Regardless you can try and simulate this circuit in LTspice and confirm there is no issue, the windings can be voltage sources to keep things simple
@@FesZElectronics I have previously built a variable high voltage power supply (50-400 V, 200 mA), for my experiments with tubes, not with an LM317, but with an FET and a transistor as a current limiter. In it I had to build a thyristor and a relay to deal with a direct short circuit.
Good idea to use LTSpice to test with 2 bridged rectifiers, I will do that.
Thanks,
Peter
Great , Thanks
Booooy, I see what you are trying to do. Are you trying to do HDC voltages for pedal tube valves? Because, if yes... damn man, I was trying a solution for that. I mean, a small circuit, small noise, high voltage dc to excited the tubes (12ax7).
Great work as usual.
Well, that was not the plan, but its a good idea! I will keep this in mind. What sort of pedals are usually built with valves? distortion or also something else?
@@FesZElectronics Hiho. Well, I'm yet a rookie working with guitar fx. As far as I am concerned we can build distortions, some audio amplifiers and sustain and compressor pedals (but compressor ones are too fancy ~to do not say complicated~)
Hello. Thanks for your nice videos. BTW 200V in 1Ohm is not 200W but 40000W at 5:45
I do not understand why you feel the need to match temperatures on the FET and regulator? done that with say totempole arrangements where you want each to have the same point on the transfer curve, but not different devices.?
The regulator has a built in over-temperature protection. I wanted to try and take advantage of that to turn off the regulator if the FET overheats
@@FesZElectronics Ahh yes, of course, that makes sense.
@@FesZElectronics Not on part 2b yet, but looking at the reference sheet, can see some omissions, like the 2.2R resistor on the output filter to limit inrush current, plus you seem to have a capacitor where it tells you specifically not to insert one, I will be very surprised if you ever get this regulating, even on part2b, we shall see, I tend not to diverge from reference designs much unless they can be calculated accurately, the guys at national will be using the best simulators and engineers to take all parameters into account, including thermal limits. When we used to do simulations, we swept lots of parameters, monty-carlo, worst case-tolerence etc, bit of a pain, but on HV circuits like this, its probably wise.
The LM317 just keeps burning the 20k ohm variable resistor!!
Sorry, but what is this supply used for?
Well, I'm not building it for a particular purpose, but its a high voltage linear supply, that can be used anywhere you need clean stabilized high voltage - one example can be in vacuum tube circuits.
@@FesZElectronics thanks
@@FesZElectronics I think I should read your coments first! xD