Difference between revisions of "Linear power supply"
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| − | A '''linear''' power supply is one that uses purely [[analog]] techniques (i.e. internal [[signal]]s with [[voltage]]s with continuously varying values) to convert input power to output, at the | + | A '''linear''' power supply is one that uses purely [[analog]] techniques (i.e. internal [[signal]]s with [[voltage]]s with continuously varying values) to convert input power to output, at the voltage needed. (The internal devices operating in this mode are said to be operating in their 'linear' mode.) |
Linear supplies are generally inefficient since if they take in a given [[current]] (at the supply voltage), then without using a [[transformer]] (which only works with [[alternating current]]), there is no easy way to produce more than that much output current (since the number of [[electron]]s in the current is fixed, and 'electrons out' must equal 'electrons in'). | Linear supplies are generally inefficient since if they take in a given [[current]] (at the supply voltage), then without using a [[transformer]] (which only works with [[alternating current]]), there is no easy way to produce more than that much output current (since the number of [[electron]]s in the current is fixed, and 'electrons out' must equal 'electrons in'). | ||
| − | Generally, the extra power (the actual amount is given by the [[ampere|amperage]] multiplied by the voltage drop from the input to the output) is discarded as heat. | + | Generally, the extra power (the actual amount is given by the [[ampere|amperage]] multiplied by the voltage drop from the input to the output) is simply discarded, as heat. |
The usual internal [[circuit]]ry is that a combination of a [[transistor]] and the load (output) are used as a voltage divider network; the [[emitter]] of the transistor is connected to the output, and the [[collector]] to the input voltage. The current through the transistor's [[base]] is adjusted so that the voltage drop across the load is as desired; the rest will be dissipated in the transistor. | The usual internal [[circuit]]ry is that a combination of a [[transistor]] and the load (output) are used as a voltage divider network; the [[emitter]] of the transistor is connected to the output, and the [[collector]] to the input voltage. The current through the transistor's [[base]] is adjusted so that the voltage drop across the load is as desired; the rest will be dissipated in the transistor. | ||
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| + | Depending on the circuit details, in linear supplies the output voltage is often dependent on the input voltage (and directly related to it), so if the former varies, so will the latter. | ||
Due to their low efficiency, in high-power applications they have generally been replaced by [[switching power supply|switching power supplies]]. | Due to their low efficiency, in high-power applications they have generally been replaced by [[switching power supply|switching power supplies]]. | ||
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Revision as of 19:26, 23 September 2018
A linear power supply is one that uses purely analog techniques (i.e. internal signals with voltages with continuously varying values) to convert input power to output, at the voltage needed. (The internal devices operating in this mode are said to be operating in their 'linear' mode.)
Linear supplies are generally inefficient since if they take in a given current (at the supply voltage), then without using a transformer (which only works with alternating current), there is no easy way to produce more than that much output current (since the number of electrons in the current is fixed, and 'electrons out' must equal 'electrons in').
Generally, the extra power (the actual amount is given by the amperage multiplied by the voltage drop from the input to the output) is simply discarded, as heat.
The usual internal circuitry is that a combination of a transistor and the load (output) are used as a voltage divider network; the emitter of the transistor is connected to the output, and the collector to the input voltage. The current through the transistor's base is adjusted so that the voltage drop across the load is as desired; the rest will be dissipated in the transistor.
Depending on the circuit details, in linear supplies the output voltage is often dependent on the input voltage (and directly related to it), so if the former varies, so will the latter.
Due to their low efficiency, in high-power applications they have generally been replaced by switching power supplies.
