Switching power supply - Revision history

Jnc: /* External links */ +well-researched column

2023-06-01T14:23:33Z

‎External links: +well-researched column

Jnc: +cat

2018-12-14T18:45:03Z

+cat

Jnc: be explicit about applicability

2018-09-28T13:25:07Z

be explicit about applicability

Jnc: Add VI coversion article

2018-09-28T00:23:55Z

Add VI coversion article

Jnc: A pretty good start

2018-09-23T18:56:07Z

A pretty good start

New page

A '''switching power supply''' is one that uses what are effectively [[digital]] techniques (i.e. internal [[signal]]s are either fully off, or fully on) to convert input power to output, at the [[voltage]] needed.

They are generally more efficient, but are also more complex, than the [[linear power supply|linear power supplies]] which preceded them. They are thus now found ubiquitously in medium- to high-power applications.

In general, all switching supplies depend on turning the input current off and on quickly; voltage regulation is achieved by leaving the input on longer when the output voltage is too low, and leaving it on for a shorter time when it is too high. Passive circuit elements such as [[capacitor]]s are used to filter out the ripple and noise from the switching.

The [[transistor]]s usually used as switches are thus operating in either fully-on or fully-off mode; they are more efficient when used in that way, contributing to the efficiency of switching supplies.

There are a wide range of design approaches in the switching supply field, depending on factors like whether isolation is needed (i.e. from wall [[alternating current|AC]], which generally requires a [[transformer]]); the relationship between the supply voltage and the output voltage; how good the voltage regulation needs to be; cost and size goals; etc, etc.

The issue with voltage is that if a power supply takes in a given [[current]] (at the supply voltage), and wishes to produce a lower output voltage, then unless it has some way to produce more than that much output current (since otherwise the number of [[electron]]s in the current is fixed, and 'electrons out' must equal 'electrons in'), the voltage difference between the two is lost energy, lowering the efficiency.

An equivalent, but inverse problem is encountered when the output voltage needs to be higher than the input. There are a number of different design approaches that can achieve voltage conversion in an efficient manner.

Isolation, regulation and voltage/amperage conversion are different objectives, but they can be achieved either separately or in concert; e.g. use of a transformer can do the first and last in one step.

One common design is to take input AC, convert it to higher [[frequency]], run that through a transformer (since transformers can be physically smaller and lighter at a higher frequency, for a given power throughput), and then convert the output to [[direct current|DC]].

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		+	* [http://www.righto.com/2012/02/apple-didnt-revolutionize-power.html Apple didn't revolutionize power supplies; new transistors did] - well-researched column which gives an overview of their history

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 They are generally more efficient, but are also more complex, than the [[linear power supply|linear power supplies]] which preceded them. They are thus now found ubiquitously in medium- to high-power applications.
-In general, all switching supplies depend on turning the input current off and on quickly; voltage regulation is achieved by leaving the input on longer when the output voltage is too low, and leaving it on for a shorter time when it is too high. Passive circuit elements such as [[capacitor]]s are used to filter out the ripple and noise from the switching.
+In general, all switching supplies depend on turning the input [[current]] off and on quickly; voltage regulation is achieved by leaving the input on longer when the output voltage is too low, and leaving it on for a shorter time when it is too high. Passive circuit elements such as [[capacitor]]s are used to filter out the ripple and noise from the switching.
 The [[transistor]]s usually used as switches are thus operating in either fully-on or fully-off mode; they are more efficient when used in that way, contributing to the efficiency of switching supplies.
@@ Line 9: / Line 9: @@
 There are a wide range of design approaches in the switching supply field, depending on factors like whether isolation is needed (i.e. from wall [[alternating current|AC]], which generally requires a [[transformer]]); the need for [[VI conversion]]; how good the voltage regulation needs to be; cost and size goals; etc, etc.
-Isolation, VI conversion, abd regulation are different objectives, but they can be achieved either separately or in concert; e.g. use of a transformer can do the first two in one step. A [[buck converter]] is often used for VI conversion.
+Isolation, VI conversion, and regulation are different objectives, but they can be achieved either separately or in concert; e.g. use of a transformer can do the first two in one step. A [[buck converter]] is often used for [[direct current|DC]] VI conversion, when going from a high voltage to a considerably lower one.
-One common design is to take input AC, convert it to higher [[frequency]], run that through a transformer (since transformers can be physically smaller and lighter at a higher frequency, for a given power throughput), and then convert the output to [[direct current|DC]].
+One common design is to take input AC, convert it to higher [[frequency]], run that through a transformer (since transformers can be physically smaller and lighter at a higher frequency, for a given power throughput), and then convert the output to DC.
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