difference between switching regulator and linear regulator?

EDAboard.com Forum Index -> Electronic Elementary Questions -> difference between switching regulator and linear regulator?

Author

Message

poovannan

Joined: 30 May 2006
Posts: 1

30 May 2006 10:33 switching regulator tutorial

what is the main differnce between switching regulator and linear regulator? for DC-DC convertor which regulator is used?send if any supporting doc present

klystron

Joined: 11 Jul 2002
Posts: 146
Helped: 4

30 May 2006 12:28 switching regulators tutorial

A linear regulator's efficiency is low < 20%) . ( the input - output voltage differential is converted to heat)
A switching regulator's efficiency is high. ( 90%)

Miguel Gaspar

Joined: 06 Mar 2006
Posts: 391
Helped: 36
Location: Culiacán, Sinaloa, Mexico

01 Jun 2006 16:11 linear regulator tutorial

A linear regulator uses a transistor in series with the load and working in his linear region, like a potentiometer, and the power is regulated at the load by varying the transistor, that works like a potentionmeter, by increasing the power in the transistor you reduce the power in the load, and by reducing the power in the transistor yo increase the power at the load. That means that the pass element, the transistor consumes a lot of power.

In The switching regulator the transistor is in series with the load, but now working in the open and saturation region, but to turno form one to another must pass by the linear region for a very small time, that are the region of small consumtion of energy.
The switching regulator need a filter to smooth the energy wave, DC, and a oscillator that provoques the switching.

dika

Joined: 03 May 2006
Posts: 74
Helped: 2

02 Jun 2006 8:18 difference between linear and switching regulator

hello miguel,
i don't understand about the linear region of transistor, can you explain more?
which type does the 78xx regulator belongs?
which type dissipate more energy?
thanks

puviarasu

Joined: 17 Dec 2004
Posts: 157
Helped: 7
Location: India

02 Jun 2006 10:36 difference between switching and linear regulator

Linear regulator works as a series resistance (potential divider) in the ckt containing the supply and load it constantly varies its value in corresponding to source and load changes. From this you can see that a part of power is wasted in the regulator as it is working as a resistor (efficiency varies according the supply voltage and the regulated voltage and current.

2) 78xx belongs to linear regulator type.

3) Linear regulator dissipates more energy.

Google
AdSense
Google Adsense

02 Jun 2006 10:36 Ads

ghaly

Joined: 19 Apr 2006
Posts: 12

02 Jun 2006 23:36 tutorial switch regulator

Hi
switching regulator has beside its higher efficiency( as mentioned before) , a higher power per unit volume i.e smaller size , and lighter weight, and because of its high frequency it has smaller capacitor values
regards

tmenet

Joined: 03 Jun 2006
Posts: 3
Helped: 1

03 Jun 2006 17:16 differentiate linear and switching regulator

poovannan and dika

The easiest way to understand the difference is to review some simple theory.

In a switching regulator transistors are turned completely ON or OFF like a switch. When they are on lots of current can flow but there is almost no voltage accross the transistor therefore the transistor dissapates very little power. When the transistor is off there is usually a voltage accross the transistor but there is no current so again there is very little power. Energy is usually stored and filtered through inductors and capacitors and regulation is controlled by varying the percentage of time on vs off. (duty cycle) The advantage to this is that there is very little heat or wasted power making this design capable of being very efficient.

In a linear regulator the transistor is turned partly on so as to provide the proper resistance to the load so that the load always sees the same voltage. Since it is partly on there is a definate voltage drop accross the regulating transistor and there is as much current simultaneously as the load is demanding. Therefore power is being dissapated accross the transistor which turns into heat. This heat is wasted power and the reason that switching supplies are so much more efficient.

The above is a simplification that doesn't take into accoount other types of losses but the discussion remains true on the fundamental difference between the two types of regulators.

I hope that clears things up.

Miguel Gaspar

Joined: 06 Mar 2006
Posts: 391
Helped: 36
Location: Culiacán, Sinaloa, Mexico

04 Jun 2006 0:50 switched linear regulator

About your questions

Quote:

hello miguel,
i don't understand about the linear region of transistor, can you explain more?
which type does the 78xx regulator belongs?
which type dissipate more energy?
thanks

For operation there are three regions of operation: Saturation, Cut and operation or linear region.
78xx are linear regulator.
Linear regulator dissipate more energy or have more losses

Sorry, but you need login in to view this attachment

jjohn

Joined: 17 Jun 2006
Posts: 275
Helped: 26

23 Jun 2006 5:33 switching regulators.docâ€

A switched-mode power supply, switch mode power supply, or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator — an internal control circuit that switches the load current rapidly on and off in order to stabilise the output voltage. Switching regulators are used as replacements for the linear regulators when higher efficiency, smaller size or lighter weight are required. They are, however, more complicated and more expensive, their switching currents can cause noise problems if not carefully suppressed, and simple designs may have a poor power factor.

SMPS can also be classified into four types according to the input and output waveforms, as follows.

* AC in, DC out: rectifier, off-line converter
* DC in, DC out: voltage converter, or current converter, or DC to DC converter
* AC in, AC out: frequency changer, cycloconverter
* DC in, AC out: inverter

AC and DC are abbreviations for alternating current and direct current.

Switched-mode PSUs in domestic products such as personal computers often have universal inputs, meaning that they can accept power from most mains supplies throughout the world, with rated frequencies from 50 Hz to 60 Hz and voltages from 100 V to 240 V (although a manual voltage "range" switch may be required). In practice they will operate from a much wider frequency range and often from a DC supply as well.

In the case of TV sets, for example, one can test the excellent regulation of the power supply by using a variac. For example, in some models made by Philips, the power supply starts when the voltage reaches around 90 volts. From there, one can change the voltage with the variac, and go as low as 40 volts and as high as 260, and the image will show absolutely no alterations.

In electronics, a linear regulator is a voltage regulator based on an active device (such as a bipolar junction transistor, field effect transistor or vacuum tube) operating in its "linear region" (in contrast, a switching regulator is based on a transistor forced to act as an on/off switch) or passive devices like zener diodes operated in their breakdown region. The regulating device is made to act like a variable resistor.

Willt

Joined: 17 Mar 2006
Posts: 78
Location: Hong Kong

23 Jun 2006 5:47 linear regulator power supply

Hi friend,

Linear regulator can only step down the input voltage while switching regulator can step up or down the input voltage. The transistor in linear regulator operates only in linear region while the transistor in switching regulator operates only in saturation and cutoff region. There are mainly two types of switching regulators: (1) inductive, (2) charge pump

(A) Linear
20-60% efficiency, very small area, very low ripple, very low EMI, lowest cost

(B) Inductive
90-95% efficiency, largest area, low ripple, moderate EMI, highest cost

(C) Charge pump
75-90% efficiency, medium area, moderate ripple, low EMI, medium cost

Tutorial from National Semiconductor could be a great help ~
http://www.national.com/AU/design/courses/253/

Will