Differences between SMPS and Linear PS

Can you tell me advantages and disadvantages between Switch Mode Power Supply and Linear Power Supply???

smps vs linear power supply

Linear

A linear regulator works by dropping a DC voltage across itself to regulate the output. This gives a nice, smooth supply and is quite efficient for lower, fairly constant currents.

However, the input is usually a rectified AC at 50 or 60Hz. For high currents, the voltage on the smoothing capacitors varies a lot, so the regulator has to drop more voltage when the AC is peaked - causing the regualtor to dissipate a lot of power.

The low frequency AC needs quite large capacitors to smooth the rectified output.

Imagine a 5V regulator passing 10A. Its input may vary from 8V to 12V with the rectified, smoothed (big capacitors!) waveform. It will then have to dissipate around 50W itself, while supplying 50W to the powered device. Only 50% efficient and a lot of heat to get rid of (big heatsinks/fans).

So, linear supplies are OK for lower currents/powers. They are trivial to make.

SMPS

In an SMPS, a transformer is driven at a much higher frequency than the mains supply, 10's to 100's of KHz. The input can be derived from rectified mains or another DC source.

The oscillator switches on and off a transistor, driving the coil. Because the transistor is just on or off, it has little voltage drop across it and therefore dissipates very little power, therefore little heatsinking is needed compared to linear supplies.

Due to the higher frequency, SMPS's also need much smaller smoothing capacitors on the final output, . Also the transformers are much smaller than similar-power mains transformers. So the supply can be much smaller and lighter than a linear supply of similar power.

SMPS's are much simpler to design for a wide range of input voltages and run at pretty much the same efficiency regardless of input voltage. Efficiencies in the region of 80% are common.

SMPS's can provide step-up, step-down and even negative output from any input.

On the down side, SMPS's are more complicated and difficult to design and so are more expensive for lower powers than linear regulators. They also tend to need a minimum current to be drawn, otherwise they can go out of regulation.

Some Links

**broken link removed**
https://www.electronics-tutorials.com/basics/switched-mode-power-supplies.htm


I forgot: linear regulators are better to use if you want a variable voltage output (like a lab supply) - SMPS's don't do variable voltage very well.

FoxyRick.

linear vs smps

FoxyRick wrote:

I forgot: linear regulators are better to use if you want a variable voltage output (like a lab supply) - SMPS's don't do variable voltage very well.

Click to expand...

This statement goes probably to far. I can show you a circuit (switchmode) which is adjustable from almost 0V dc to 100V dc with adjustable current limt from 0.1A to 25A..you will have difficulty in finding similar linear equivalent unless you would like to have a heater..

smps vs linear

Also I use HP power supply device with adjustable output 0-60 VDC and current limit 0-35ADC.

characteristics of smps vs linear power supply

IanP said:

FoxyRick wrote:

I forgot: linear regulators are better to use if you want a variable voltage output (like a lab supply) - SMPS's don't do variable voltage very well.

Click to expand...

This statement goes probably to far. I can show you a circuit (switchmode) which is adjustable from almost 0V dc to 100V dc with adjustable current limt from 0.1A to 25A..you will have difficulty in finding similar linear equivalent unless you would like to have a heater..

Click to expand...

Hi IanP, do you mind to share with us the circuit? My appreciate.

linear regulator versus smps

SMPS = High switching noise
LINEAR= Low noise and tight regulation

sometimes Linear power supplies are prefered in low noise applications

very low noise smps design

Attached is *.gif file of a scanned (terrible copy) schematic of the 100V SM power supply that I built 12 years ago for an echosounder mounted on a dredge.
It is based on pretty unusual concept: regulation occurs on the negative line!

linear transformer vs smps

first of all i dont understand the following line you said

It is based on pretty unusual concept: regulation occurs on the negative line!

Click to expand...

can you explain this???

and secondly can you make a neat schematic of this circuit on a software because some parts of this diagram are not clearly visible.

laboratory smps circuit

OK, I stand (actually sit) corrected on the variable SMPS, although I still say that it's easier to do with a linear

However, there is an article in January's Elektor about CUK convertors, and a project to build a variable CUK PSU with 0V to 100V, 5A output - quite impressive and well worth a look.

Cheers,
FoxyRick.

lab power supply schematic smps

FoxyRick can you please upload that article???

step response of smps

FoxyRick wrote
However, there is an article in January's Elektor about CUK convertors, and a project to build a variable CUK PSU with 0V to 100V, 5A output - quite impressive and well worth a look.

Click to expand...

It is in which year issue, can u upload the article.
Thanx in advance
rauol

smps vs linear surge performance

Linear: low efficiency, low ripper noise,step down,compact
SMPS: high efficiency, high noise,step down/up

basics of smps

hi all;
you can fined very good information on this site
https://www.onsemi.com/
www.natinoal.com

thank you

linear adaptor vs smps

liniear:
high dissipation
big size
simple
economies
switcing:
low dissipation (high efficient)
size depent on power to generate but less then liniear
complicated
expensive to build

why smps is used instead of linear

Linear supplys faster than switching supplys.

smps for lab

In my opinion linear power supplies are better if you need universal and accurate laboratory power source even if the price paid for that is low efficiency. However it is also possible to combine two types of power supplies in one system: SMPS + linear to minimize power losses. But one should keep in mind that any SMPS increase noise levels which may be unacceptable in many analog applications.

100v 25a edaboard

usually spms are used for high currents/voltages... in fact, they tend to be more efficient on heavy loads, oposite to linear ....

lab smps

This statement goes probably to far. I can show you a circuit (switchmode) which is adjustable from almost 0V dc to 100V dc with adjustable current limt from 0.1A to 25A..you will have difficulty in finding similar linear equivalent unless you would like to have a heater..

Click to expand...

There is concern about step response in such smps which is much worse than in linear ones. For such purpose as laboratory power supply it is recommended to use linear power supply regardless of the power dissipated. Any interferences generated by smps may cause very sensitive circuits go crazy [/quote]

power supply vs smps

hi IanP
plz upload more information about your circuit.