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Technoramble: Power Supplies
14 years ago
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Another long-winded babbling about technology in your life.
Today, those little warts, bricks, cables, and things you plug into the wall to charge your phone, run your radio, and fap to dirty pictures on FA with--
POWER SUPPLIES!
The under-appreciated workhorse of our digital world.
There's two common kinds of power supplies, linear and switch-mode supplies.
First, let's talk about linear supplies.
These are very simple affairs, and are easy to understand.
AC power comes into a transformer, which steps the voltage to a ballpark-figure close to what is desired - still AC. A rectifier - usually a set of diodes - convert this AC into a rapidly pulsing DC. We still can't use this though, so filters - usually a capacitor - are added to filter this down into a stable DC supply. Finally, a regulator clamps the final output to a strict DC output that can do whatever you ask of it.
Linear power supplies are generally rugged, and have a comparatively low incidence of failure. They also kick out very little electrical noise, and the filter tends to screen out most noise that's coming in on the power line. When one does fail, it's usually either the regulator or the filter-caps.
Switch-mode power supplies - commonly called "switchers" for short - are a lot more complicated than linear supplies, and were created to address a few of their shortcomings.
Incoming power is immediately rectified and filtered to create a high-voltage DC power line, which feeds a very high frequency "chopper" circuit. The chopper feeds a transformer, then the HF power feed's re-rectified and re-filtered before finally being passed into the regulators for output.
Switchers have gotten maddeningly popular because of a few advantages over linear supplies - efficiency, adaptability, and size.
Despite the many steps in a switcher compared to a linear supply, by running at such a high frequency the switcher can realize incredible efficiency. A lot less power is lost in the transformer by running it at such high frequency over the comparatively low frequencies of incoming line.
The chopper circuit can also be designed with a feedback system, that tells it if it needs to adjust its output up or down. This allows a switcher to be able to automatically adjust to varying input voltages without any effect on output.
Higher frequency power can be put through very small transformers, compared to line-frequency power. It's also a lot easier to filter with capacitors. Combine these two, and you have a dramatically smaller power supply, even in the face of needing so many components.
Unfortunately, switchers have their drawbacks, and as such linear supplies haven't died yet.
One of the biggest things is noise. Despite the ease of filtering out of the DC line itself, sensitive analog devices - such as radios - need the cleaner output of a linear supply. You'd be able to hear the buzz of the switching frequency in your radio otherwise.
Another is shorter life expectancy. Inherently, adding more components adds more areas to fail - especially those fail-happy capacitors. As the main capacitors begin to fail, they affect the chopper circuit, lowering its frequency. This reduces overall performance of the supply. By time this gets low enough for a human ear to hear it, the supply's already degraded badly and should be considered "about to fail".
Regardless of what kind of power supply you have, you can help extend its life by unplugging it when you aren't using it. Keeping all those parts energized unloaded can actually harm some higher power supplies, and it also causes undue wear on all the components that could easily be prevented. Add in that you're powering something that's doing literally nothing - save juice, save your power supplies, unplug when not in use!
Also, pay attention to the rating of the supply, versus the thing you're powering. Overloading any power supply is very damaging, especially to switchers. I've destroyed one completely through an extended overload. Not that linear supplies are immune! I've melted a wall-wart supply down through an extended overload condition.
I hope I've shed some light on this complicated topic in a way you can understand, and given you a new appreciation for this tireless workforce.
Today, those little warts, bricks, cables, and things you plug into the wall to charge your phone, run your radio, and fap to dirty pictures on FA with--
POWER SUPPLIES!
The under-appreciated workhorse of our digital world.
There's two common kinds of power supplies, linear and switch-mode supplies.
First, let's talk about linear supplies.
These are very simple affairs, and are easy to understand.
AC power comes into a transformer, which steps the voltage to a ballpark-figure close to what is desired - still AC. A rectifier - usually a set of diodes - convert this AC into a rapidly pulsing DC. We still can't use this though, so filters - usually a capacitor - are added to filter this down into a stable DC supply. Finally, a regulator clamps the final output to a strict DC output that can do whatever you ask of it.
Linear power supplies are generally rugged, and have a comparatively low incidence of failure. They also kick out very little electrical noise, and the filter tends to screen out most noise that's coming in on the power line. When one does fail, it's usually either the regulator or the filter-caps.
Switch-mode power supplies - commonly called "switchers" for short - are a lot more complicated than linear supplies, and were created to address a few of their shortcomings.
Incoming power is immediately rectified and filtered to create a high-voltage DC power line, which feeds a very high frequency "chopper" circuit. The chopper feeds a transformer, then the HF power feed's re-rectified and re-filtered before finally being passed into the regulators for output.
Switchers have gotten maddeningly popular because of a few advantages over linear supplies - efficiency, adaptability, and size.
Despite the many steps in a switcher compared to a linear supply, by running at such a high frequency the switcher can realize incredible efficiency. A lot less power is lost in the transformer by running it at such high frequency over the comparatively low frequencies of incoming line.
The chopper circuit can also be designed with a feedback system, that tells it if it needs to adjust its output up or down. This allows a switcher to be able to automatically adjust to varying input voltages without any effect on output.
Higher frequency power can be put through very small transformers, compared to line-frequency power. It's also a lot easier to filter with capacitors. Combine these two, and you have a dramatically smaller power supply, even in the face of needing so many components.
Unfortunately, switchers have their drawbacks, and as such linear supplies haven't died yet.
One of the biggest things is noise. Despite the ease of filtering out of the DC line itself, sensitive analog devices - such as radios - need the cleaner output of a linear supply. You'd be able to hear the buzz of the switching frequency in your radio otherwise.
Another is shorter life expectancy. Inherently, adding more components adds more areas to fail - especially those fail-happy capacitors. As the main capacitors begin to fail, they affect the chopper circuit, lowering its frequency. This reduces overall performance of the supply. By time this gets low enough for a human ear to hear it, the supply's already degraded badly and should be considered "about to fail".
Regardless of what kind of power supply you have, you can help extend its life by unplugging it when you aren't using it. Keeping all those parts energized unloaded can actually harm some higher power supplies, and it also causes undue wear on all the components that could easily be prevented. Add in that you're powering something that's doing literally nothing - save juice, save your power supplies, unplug when not in use!
Also, pay attention to the rating of the supply, versus the thing you're powering. Overloading any power supply is very damaging, especially to switchers. I've destroyed one completely through an extended overload. Not that linear supplies are immune! I've melted a wall-wart supply down through an extended overload condition.
I hope I've shed some light on this complicated topic in a way you can understand, and given you a new appreciation for this tireless workforce.
