7 ms·

A half century ago, better transistors revolutionized computer power supplies

112 points by kens 7y ago

analog31 7y ago
Interestingly, the same transistors have revolutionized audio amplifiers. I'm a musician, and typically play with an amplifier. Over the years, my amp has gone from 40 pounds of steel, copper, and vacuum tubes, to a 15 pound solid state amplifier, to a 2.5 pound switchmode amp, with no loss of tone quality that I can perceive. The rise of the new "micro" amplifiers has been driven in no small part by improved MOSFETs that can switch faster and more efficiently, at higher voltages. I can't imagine that demand for musical equipment drove this development, but we certainly benefit from it.
- hdiriekei 7y ago
  Quality micro amplifiers (class D) are extremely difficult to design. They are way outside the possibilities of amateurs or boutique shops, unlike classical amps (class A, ...)
  - baybal2 7y ago
    > They are way outside the possibilities of amateurs or boutique shops I disagree, take a look at what that guy does: https://twitter.com/amiteque https://twitter.com/amiteque
  - kragen 7y ago
    What are the pitfalls?
    - analog31 7y ago
      Owning a good enough oscilloscope is actually an issue. The switching signals are high speed, and subtle variations impinge on both the efficiency and stability of the amplifier. Many of the components are operating in their regime of non ideal behavior, e.g., a capacitor is not just a capacitor. Circuit board layout is also a big deal. Even the commercial amplifier makers have mostly reverted to buy-in modules. Most of the "mini amps" sold for bass guitar contain IcePower modules made by a division of Bang & Olufsen. I've gone so far as to simulate a switchmode amplifier in LTSpice just for fun. I'm quite heavily into electronics, but have made it a personal rule not to mess around with homemade line powered equipment that I would actually take to a performance. I don't want to become known as the whiz kid whose homemade gear blew up on stage. ;-) At lower power levels, there are some IC's made by Texas Instruments and others that shouldn't be too difficult to apply, but you can also get entire amplifier boards with these chips from online suppliers for next to nothing.
      - nwallin 7y ago
        Define "good enough oscilloscope"? A rigol 1054z can be had for $4-500. What do you need from an oscilloscope that the 1054z doesn't provide? I'm not saying you're wrong, I just don't understand.
        analog31 7y ago
        That's probably good enough, but certainly better than what I have at home. In fact, I bought a couple of those for my workplace.
      - rasz 7y ago
        How is owning an oscilloscope capable of <~50KHz BW an issue? Those are the only frequencies you should be worried about in an audio amp.
        detaro 7y ago
        Not for testing a class-D amp, which switches in the MHz range, and you do want to test if it's stable, if your filters actually get rid of the HF parts, ... And even for an analog design 50kHz wouldn't really be enough for many potential problems which happen above that. Worrying just about the audio range is not enough.
        analog31 7y ago
        Indeed, and it's the high frequency behavior where you see if you're getting charge on and off the gates of the MOSFETs fast enough with just the right timing.
- unlinked_dll 7y ago
  Also a guitarist. I own 3 amps, two tube and one hybrid. Used to have a solid state. You really can't tell the difference? It's night and day to me, even with the newer Fender mustangs that have great models. I won't turn in my HT40 for a solid state until Kempers can deliver the same quality at the same price (which I picked up off craigslist for $400). Now my little mono price 15W (which is loud as hell) sounds pretty terrible in most settings but I haven't found a solid state that can give the same character with the right settings. Plus real spring reverb, i can't kick a DSP to make it jangle. If you're talking acoustic sure solid state wins every day of the week. But in the mid tier amp market for electrics tubes win out. I do think though that most people don't know how to use a tube amp to get a good tone though. Crank the power amp volume and use your gain as a volume control, push the input with a clean boost or light drive to get distortion. The harmonics stack through the chain, and that's how you get the crystal clear sound without being drowned in noise or fuzz. It's also something you can't do on a solid state, since the input is buffered and the DSPs don't really handle that idea well.
  - analog31 7y ago
    I'm just an upright bassist. I firmly believe that DSP could emulate any guitar amp. If it's real, then it can be measured, and if it can be measured, then it can be simulated. What I think is the big deal is, an amp might be capable of producing a certain tone quality, but that tone quality is unreachable if the controls don't cooperate or are not intuitive. It's a user interface problem. What's more, if it's frustrating to the guitarist, they will notice even if the audience (or the bassist) doesn't. I also think it's a non-problem to some extent because tubes are not prohibitively expensive, and guitar amps don't need to be exceptionally powerful.
    - nullc 7y ago
      > I firmly believe that DSP could emulate any guitar amp. If it's real, then it can be measured, and if it can be measured, then it can be simulated. This is absolutely true, but the possibility of it doesn't tell you anything about someone having been successful at it. One way to think about is that the market for the product can be split into three populations: Those who will buy even if the simulation is poor (they can't tell, don't care, or buy based on price or other wizbang features), those who won't buy no matter how good the simulation is (they don't care about the cost/weight/power, are happy with the classic stuff, ones snub simulations for social reasons, ones who prefer products without long boot times or with physical knobs, or just can't tell and are going to be conservative), and those who would buy but only if it's good. I think in many cases this last group is much smaller than the other two. As a result it doesn't necessarily make commercial sense to make the simulation especially good. Even in the case of linear effects (e.g. typically reverbs) where it's easy to measure them and determine scientifically that any difference would be (nearly-)inaudible there are many implementations that don't even bother to try being particularly faithful. For non-linear effects like guitar amplifiers it's much more difficult to objectively characterize their performance. [I own no tube amps or other similar things, but I understand why people do.]
- dreamcompiler 7y ago
  Class D (or Class T) amplifiers are just switching power supplies "turned sideways." By which I mean that the important input changes from the AC power to the regulation signal. The latter is a DC reference voltage in a power supply; it's the audio input in an amp.
Retric 7y ago
A related advancement is handheld car jump-starters have gotten cheap and tiny. They frequently include USB charging ports etc due to those same transistor advancements coupled with improved battery technology.
- mrfusion 7y ago
  So I don’t have to carry cables anymore?
  - Gibbon1 7y ago
    Yeah a hand held jump starter is like $40-60. I have one that was left in my car when it got recovered after being stolen. Works great. Also doubles as a USB charger and flashlight.
    - dylan604 7y ago
      >Works great. As long as it has enough charge to do its job when required. What type of batteries are in these, and how long do they hold appropriate charges? I've seen these smaller starters in stores that I immediately dismiss them as useful (dollar stores etc).
      - Gibbon1 7y ago
        What I found is that if the car battery is completely dead they don't work. So they aren't a complete replacement for jumper cables. But I've left the lights on, battery dead. And the hand held jumper got my van started. I don't know how long the batteries last. I assume they use lithium polymer batteries. Mine I just keep it plugged in all the time.
        jacquesm 7y ago
        Let it sit for a few minutes before attempting to crank the car otherwise the starter motor and the battery are in competition and that leaves too little for the starter motor. First you need to bring the battery up to a voltage higher than what's left under maximum load by the starter motor. 10V should do it for most cars.
ChuckMcM 7y ago
They are marvels, and today's MOSFETs make for even smaller and lighter supplies. They bring noise with them though, so you will often see switching supplies that take line voltage down to some lower DC voltage, and then a crap ton of filters, connected to a linear supply that gives you the desired voltage in RF circuits.
pjc50 7y ago
There have been subsequent revolutions too: the silicon carbide MOSFET, which supports much higher voltages, and the IGBT (integrated gate bipolar transistor), which have done the same thing for much larger power electronics such as those in electric cars. Switchmode power supplies have also benefited from better microprocessors allowing control of temperature, peak current, etc; my employer has done some neat tricks integrating this into audio amplifiers for phones. https://www.cirrus.com/company/media-center/releases/2019/cirrus-logic-introduces-industrys-smallest-low-power-boosted-smart-audio-amplifier-to-support-global-shift-to-mobile-stereo/ https://www.cirrus.com/company/media-center/releases/2019/ci...
- kragen 7y ago
  *insulated
Gibbon1 7y ago
Definitely power transistors are one of the most important developments of the last 50 years that most people don't know about. They enabled not just computer power supplies but also variable frequency drives for electric motors. That saved enormous amount of energy. And made things like electric cars practical.
hristov 7y ago
Currently there is a new wave of better transistor technology, that should hopefully make our power supplies better. For example, Gallium Nitride transistors in combination with System in Package technology and spintronic isolators could and should revolutionize consumer power supplies again. Unfortunately, this area is not considered too sexy and does not get too much investment. But hopefully, they do get around to it. I can't wait to get rid of the power bricks.
- kragen 7y ago
  Ken mentioned GaN in the article.
- baybal2 7y ago
  > Unfortunately, this area is not considered too sexy and does not get too much investment. You are getting it better than the rest of the world. Power electronics is once of the last semiconductor niche where US has both the edge in already, and a prospect for future growth. You have to thank your military for that. Military use power electronics is a giant market in USA, but it's also a very pathological one. US military buys simplest bucks and boost circuits (for non-engineers, those things amount to "power electronics 101") for few thousand dollars a pop. Few months ago, I had a chat with BYD engineers about their own power electronics problem. The best China got domestically are few generations old IGBTs. E6 for example has a 89% efficient powertrain, as I was told. The only Chinese power electronics company on the road to SiC I know is IVCT, and I haven't seen them showing any life signs for quite some time. They want to eventually do their own power electronics, or at least fully own it from the packaging/integration stage. You can see how far Tesla went in Model S to Model 3 inverter design when they switched to SiC switches. Model 3's inverter is microscopic in comparison to Model S ones. And apparently, it's also more efficient at the same time, without any extra tricks used.
  - lisk1 7y ago
    Probably the thing you dont know about Model 3 motor inverter is that its designed by a Dutch company and uses ST Microelectronics power mosfets manufactured in fab in Italy , Tesla is also considering second supplier for power mosfets, Infinion technology again European based electronics components manufacturing company.
jacquesm 7y ago
Ditto for welding equipment. A switched mode stick welder weighs next to nothing and will happily max out whatever socket you plug it in to. Steady as can be too under fluctuating load.
Stierlitz 7y ago
“Instead of a conventional linear power supply, Holt built one like those used in oscilloscopes. It switched the power on and off not sixty times per second, but thousands of times; this allowed it to store the power for far less time, and thus throw off less heat.” Not exactly, the power is stored in an inductor and fed to the load, the inductor being topped-up by switching the unregulated rail on-and-off thousands of times a second.
Animats 7y ago
Switching power supplies are a simple idea complicated to do well. The concept is an inductor and a switch across the input. Close the switch, and the inductor's magnetic field builds up. Open the switch, and the inductor tries to maintain constant current by producing a high voltage. If the input side inductor is part of a transformer, you can get a higher or lower voltage out as the magnetic field collapses. That's an auto ignition from the mid 20th century. That approach suffers from arcing at the switch points, blithers all over the RF spectrum, and wastes energy by keeping the input on too long. Progress since then focuses on solving all those problems, plus some others. Power MOSFETs provided an electronic switch with a really low ON resistance, in the millohm range, an OFF resistance in the kiloohm or even megohm range, and a switching time fast enough that you don't spend much time between ON and OFF. At very low resistance, almost no energy is dissipated in the switch, and at very high resistance, almost no energy is dissipated in the switch. Between those points, the switch loses energy through resistive heating. This is why switching power supplies get warm. The less time spent transitioning between OFF and ON, the less heating. A switching power supply is almost a dead short across its input if the switch stays turned on after the inductor reaches magnetic saturation. This is why switching power supplies can burn up or catch fire. Failure of the power MOSFET (and they usually fail ON) or the control circuitry is big trouble. Which is why they need protection circuitry. This is what UL approval is for. Along with insisting that the input and output windings of the power transformer have enough insulation between them, so you don't get power line voltage at the USB jack. In most other areas of electronics, you avoid generating spikes. Switching power supplies generate big spikes on purpose. Getting the energy of those spikes into the output capacitor is what it's all about. The energy can leak out as spikes on the input side, spikes on the output side, loud RF noise, or heat. Getting all those under control requires some extra parts. Surface mount ferrite beads and chip capacitors, mostly. Things you usually don't have to think about, such as the inductance of capacitors, are big issues. This is what FCC approval is for. I designed and built a special purpose switching power supply a few years ago, and it's on Github. [1] There's a detailed explanation of how it works, including what all those minor parts do. The traditional linear solution to that problem is about 5% efficient, runs hot, and much larger. [1] https://github.com/John-Nagle/ttyloopdriver https://github.com/John-Nagle/ttyloopdriver
fortran77 7y ago
> As a tech enthusiast, you probably know what microprocessor is in your computer and how much physical memory it has, but odds are you know nothing about the power supply. Ummm...tech "enthusiasts" generally spend a lot of time choosing the power supply if building a PC!
rwallace 7y ago
> For example, in 1962 the Telstar satellite (the first satellite to transmit television pictures) and the Minuteman missile both used switching power supplies. I thought switching power supplies were for converting high voltage AC to low voltage DC. I would have expected a satellite to run off solar panels and missile electronics to run off batteries, both of which already produce low voltage DC. What am I missing?
- colanderman 7y ago
  SMPSes are also used for DC/DC conversion (up or down). Especially with solar panels, they are mixed current/voltage-mode devices, so you want to load them at a specific voltage (which depends on the incident light) to maximize the power draw. (This is what a power optimizer does in a solar panel installation.)

112 points by kens 7y ago

Interestingly, the same transistors have revolutionized audio amplifiers. I'm a musician, and typically play with an amplifier. Over the years, my amp has gone from 40 pounds of steel, copper, and vacuum tubes, to a 15 pound solid state amplifier, to a 2.5 pound switchmode amp, with no loss of tone quality that I can perceive. The rise of the new "micro" amplifiers has been driven in no small part by improved MOSFETs that can switch faster and more efficiently, at higher voltages. I can't imagine that demand for musical equipment drove this development, but we certainly benefit from it.

hdiriekei 7y ago
Quality micro amplifiers (class D) are extremely difficult to design. They are way outside the possibilities of amateurs or boutique shops, unlike classical amps (class A, ...)
- baybal2 7y ago
  > They are way outside the possibilities of amateurs or boutique shops I disagree, take a look at what that guy does: https://twitter.com/amiteque https://twitter.com/amiteque
- kragen 7y ago
  What are the pitfalls?
  - analog31 7y ago
    Owning a good enough oscilloscope is actually an issue. The switching signals are high speed, and subtle variations impinge on both the efficiency and stability of the amplifier. Many of the components are operating in their regime of non ideal behavior, e.g., a capacitor is not just a capacitor. Circuit board layout is also a big deal. Even the commercial amplifier makers have mostly reverted to buy-in modules. Most of the "mini amps" sold for bass guitar contain IcePower modules made by a division of Bang & Olufsen. I've gone so far as to simulate a switchmode amplifier in LTSpice just for fun. I'm quite heavily into electronics, but have made it a personal rule not to mess around with homemade line powered equipment that I would actually take to a performance. I don't want to become known as the whiz kid whose homemade gear blew up on stage. ;-) At lower power levels, there are some IC's made by Texas Instruments and others that shouldn't be too difficult to apply, but you can also get entire amplifier boards with these chips from online suppliers for next to nothing.
    - nwallin 7y ago
      Define "good enough oscilloscope"? A rigol 1054z can be had for $4-500. What do you need from an oscilloscope that the 1054z doesn't provide? I'm not saying you're wrong, I just don't understand.
      - analog31 7y ago
        That's probably good enough, but certainly better than what I have at home. In fact, I bought a couple of those for my workplace.
    - rasz 7y ago
      How is owning an oscilloscope capable of <~50KHz BW an issue? Those are the only frequencies you should be worried about in an audio amp.
      - detaro 7y ago
        Not for testing a class-D amp, which switches in the MHz range, and you do want to test if it's stable, if your filters actually get rid of the HF parts, ... And even for an analog design 50kHz wouldn't really be enough for many potential problems which happen above that. Worrying just about the audio range is not enough.
        analog31 7y ago
        Indeed, and it's the high frequency behavior where you see if you're getting charge on and off the gates of the MOSFETs fast enough with just the right timing.
unlinked_dll 7y ago
Also a guitarist. I own 3 amps, two tube and one hybrid. Used to have a solid state. You really can't tell the difference? It's night and day to me, even with the newer Fender mustangs that have great models. I won't turn in my HT40 for a solid state until Kempers can deliver the same quality at the same price (which I picked up off craigslist for $400). Now my little mono price 15W (which is loud as hell) sounds pretty terrible in most settings but I haven't found a solid state that can give the same character with the right settings. Plus real spring reverb, i can't kick a DSP to make it jangle. If you're talking acoustic sure solid state wins every day of the week. But in the mid tier amp market for electrics tubes win out. I do think though that most people don't know how to use a tube amp to get a good tone though. Crank the power amp volume and use your gain as a volume control, push the input with a clean boost or light drive to get distortion. The harmonics stack through the chain, and that's how you get the crystal clear sound without being drowned in noise or fuzz. It's also something you can't do on a solid state, since the input is buffered and the DSPs don't really handle that idea well.
- analog31 7y ago
  I'm just an upright bassist. I firmly believe that DSP could emulate any guitar amp. If it's real, then it can be measured, and if it can be measured, then it can be simulated. What I think is the big deal is, an amp might be capable of producing a certain tone quality, but that tone quality is unreachable if the controls don't cooperate or are not intuitive. It's a user interface problem. What's more, if it's frustrating to the guitarist, they will notice even if the audience (or the bassist) doesn't. I also think it's a non-problem to some extent because tubes are not prohibitively expensive, and guitar amps don't need to be exceptionally powerful.
  - nullc 7y ago
    > I firmly believe that DSP could emulate any guitar amp. If it's real, then it can be measured, and if it can be measured, then it can be simulated. This is absolutely true, but the possibility of it doesn't tell you anything about someone having been successful at it. One way to think about is that the market for the product can be split into three populations: Those who will buy even if the simulation is poor (they can't tell, don't care, or buy based on price or other wizbang features), those who won't buy no matter how good the simulation is (they don't care about the cost/weight/power, are happy with the classic stuff, ones snub simulations for social reasons, ones who prefer products without long boot times or with physical knobs, or just can't tell and are going to be conservative), and those who would buy but only if it's good. I think in many cases this last group is much smaller than the other two. As a result it doesn't necessarily make commercial sense to make the simulation especially good. Even in the case of linear effects (e.g. typically reverbs) where it's easy to measure them and determine scientifically that any difference would be (nearly-)inaudible there are many implementations that don't even bother to try being particularly faithful. For non-linear effects like guitar amplifiers it's much more difficult to objectively characterize their performance. [I own no tube amps or other similar things, but I understand why people do.]
dreamcompiler 7y ago
Class D (or Class T) amplifiers are just switching power supplies "turned sideways." By which I mean that the important input changes from the AC power to the regulation signal. The latter is a DC reference voltage in a power supply; it's the audio input in an amp.

Retric 7y ago

A related advancement is handheld car jump-starters have gotten cheap and tiny. They frequently include USB charging ports etc due to those same transistor advancements coupled with improved battery technology.

mrfusion 7y ago
So I don’t have to carry cables anymore?
- Gibbon1 7y ago
  Yeah a hand held jump starter is like $40-60. I have one that was left in my car when it got recovered after being stolen. Works great. Also doubles as a USB charger and flashlight.
  - dylan604 7y ago
    >Works great. As long as it has enough charge to do its job when required. What type of batteries are in these, and how long do they hold appropriate charges? I've seen these smaller starters in stores that I immediately dismiss them as useful (dollar stores etc).
    - Gibbon1 7y ago
      What I found is that if the car battery is completely dead they don't work. So they aren't a complete replacement for jumper cables. But I've left the lights on, battery dead. And the hand held jumper got my van started. I don't know how long the batteries last. I assume they use lithium polymer batteries. Mine I just keep it plugged in all the time.
      - jacquesm 7y ago
        Let it sit for a few minutes before attempting to crank the car otherwise the starter motor and the battery are in competition and that leaves too little for the starter motor. First you need to bring the battery up to a voltage higher than what's left under maximum load by the starter motor. 10V should do it for most cars.

ChuckMcM 7y ago

They are marvels, and today's MOSFETs make for even smaller and lighter supplies. They bring noise with them though, so you will often see switching supplies that take line voltage down to some lower DC voltage, and then a crap ton of filters, connected to a linear supply that gives you the desired voltage in RF circuits.

pjc50 7y ago

There have been subsequent revolutions too: the silicon carbide MOSFET, which supports much higher voltages, and the IGBT (integrated gate bipolar transistor), which have done the same thing for much larger power electronics such as those in electric cars. Switchmode power supplies have also benefited from better microprocessors allowing control of temperature, peak current, etc; my employer has done some neat tricks integrating this into audio amplifiers for phones. https://www.cirrus.com/company/media-center/releases/2019/cirrus-logic-introduces-industrys-smallest-low-power-boosted-smart-audio-amplifier-to-support-global-shift-to-mobile-stereo/ https://www.cirrus.com/company/media-center/releases/2019/ci...

kragen 7y ago
*insulated

Gibbon1 7y ago

Definitely power transistors are one of the most important developments of the last 50 years that most people don't know about. They enabled not just computer power supplies but also variable frequency drives for electric motors. That saved enormous amount of energy. And made things like electric cars practical.

hristov 7y ago

Currently there is a new wave of better transistor technology, that should hopefully make our power supplies better. For example, Gallium Nitride transistors in combination with System in Package technology and spintronic isolators could and should revolutionize consumer power supplies again. Unfortunately, this area is not considered too sexy and does not get too much investment. But hopefully, they do get around to it. I can't wait to get rid of the power bricks.

kragen 7y ago
Ken mentioned GaN in the article.
baybal2 7y ago
> Unfortunately, this area is not considered too sexy and does not get too much investment. You are getting it better than the rest of the world. Power electronics is once of the last semiconductor niche where US has both the edge in already, and a prospect for future growth. You have to thank your military for that. Military use power electronics is a giant market in USA, but it's also a very pathological one. US military buys simplest bucks and boost circuits (for non-engineers, those things amount to "power electronics 101") for few thousand dollars a pop. Few months ago, I had a chat with BYD engineers about their own power electronics problem. The best China got domestically are few generations old IGBTs. E6 for example has a 89% efficient powertrain, as I was told. The only Chinese power electronics company on the road to SiC I know is IVCT, and I haven't seen them showing any life signs for quite some time. They want to eventually do their own power electronics, or at least fully own it from the packaging/integration stage. You can see how far Tesla went in Model S to Model 3 inverter design when they switched to SiC switches. Model 3's inverter is microscopic in comparison to Model S ones. And apparently, it's also more efficient at the same time, without any extra tricks used.
- lisk1 7y ago
  Probably the thing you dont know about Model 3 motor inverter is that its designed by a Dutch company and uses ST Microelectronics power mosfets manufactured in fab in Italy , Tesla is also considering second supplier for power mosfets, Infinion technology again European based electronics components manufacturing company.

jacquesm 7y ago

Ditto for welding equipment. A switched mode stick welder weighs next to nothing and will happily max out whatever socket you plug it in to. Steady as can be too under fluctuating load.

Stierlitz 7y ago

“Instead of a conventional linear power supply, Holt built one like those used in oscilloscopes. It switched the power on and off not sixty times per second, but thousands of times; this allowed it to store the power for far less time, and thus throw off less heat.” Not exactly, the power is stored in an inductor and fed to the load, the inductor being topped-up by switching the unregulated rail on-and-off thousands of times a second.

Animats 7y ago

Switching power supplies are a simple idea complicated to do well. The concept is an inductor and a switch across the input. Close the switch, and the inductor's magnetic field builds up. Open the switch, and the inductor tries to maintain constant current by producing a high voltage. If the input side inductor is part of a transformer, you can get a higher or lower voltage out as the magnetic field collapses. That's an auto ignition from the mid 20th century. That approach suffers from arcing at the switch points, blithers all over the RF spectrum, and wastes energy by keeping the input on too long. Progress since then focuses on solving all those problems, plus some others. Power MOSFETs provided an electronic switch with a really low ON resistance, in the millohm range, an OFF resistance in the kiloohm or even megohm range, and a switching time fast enough that you don't spend much time between ON and OFF. At very low resistance, almost no energy is dissipated in the switch, and at very high resistance, almost no energy is dissipated in the switch. Between those points, the switch loses energy through resistive heating. This is why switching power supplies get warm. The less time spent transitioning between OFF and ON, the less heating. A switching power supply is almost a dead short across its input if the switch stays turned on after the inductor reaches magnetic saturation. This is why switching power supplies can burn up or catch fire. Failure of the power MOSFET (and they usually fail ON) or the control circuitry is big trouble. Which is why they need protection circuitry. This is what UL approval is for. Along with insisting that the input and output windings of the power transformer have enough insulation between them, so you don't get power line voltage at the USB jack. In most other areas of electronics, you avoid generating spikes. Switching power supplies generate big spikes on purpose. Getting the energy of those spikes into the output capacitor is what it's all about. The energy can leak out as spikes on the input side, spikes on the output side, loud RF noise, or heat. Getting all those under control requires some extra parts. Surface mount ferrite beads and chip capacitors, mostly. Things you usually don't have to think about, such as the inductance of capacitors, are big issues. This is what FCC approval is for. I designed and built a special purpose switching power supply a few years ago, and it's on Github. [1] There's a detailed explanation of how it works, including what all those minor parts do. The traditional linear solution to that problem is about 5% efficient, runs hot, and much larger. [1] https://github.com/John-Nagle/ttyloopdriver https://github.com/John-Nagle/ttyloopdriver

fortran77 7y ago

> As a tech enthusiast, you probably know what microprocessor is in your computer and how much physical memory it has, but odds are you know nothing about the power supply. Ummm...tech "enthusiasts" generally spend a lot of time choosing the power supply if building a PC!

rwallace 7y ago

> For example, in 1962 the Telstar satellite (the first satellite to transmit television pictures) and the Minuteman missile both used switching power supplies. I thought switching power supplies were for converting high voltage AC to low voltage DC. I would have expected a satellite to run off solar panels and missile electronics to run off batteries, both of which already produce low voltage DC. What am I missing?

colanderman 7y ago
SMPSes are also used for DC/DC conversion (up or down). Especially with solar panels, they are mixed current/voltage-mode devices, so you want to load them at a specific voltage (which depends on the incident light) to maximize the power draw. (This is what a power optimizer does in a solar panel installation.)