LDO DC Circuit

TYPES OF LOWERING DC VOLTAGE REGULATOR

Regular regulator

The usual regulators include 78 ** ic generation (eg, 7805, 7809, etc.), or it can use a transistor and zener (eg as in the picture)

The advantages of this type of regulator is cheap and simple, but the ability of the power / current is very dependent on the ability of the active components. When the load is too high, then the active component will be overheating and usually the output voltage will drop. 
So the ability regulator of this type is limited to the ability of the active components. For example it is only able to supply a maximum of 1A at its output to its input although there is a current of 10A. 
Another picture from the usual regulator, 7805 (from outside sources).

Regulators Low Drop Output (LDO)

Due to current limitations on the regulator at the top, then the regulator system developed by Low Drop Output (LDO), which is a system that is "censoring" the output voltage. The goal is that the output voltage can be stabilized, so LDO will know how much power is removed and when the output goes down then the LDO will automatically raise its output, so we get a stable output with drop / fall slightly. Because the output voltage censored and automatically locked, then it can be programmed LDO output (regulated output voltage as you wish).There are 2 types of LDO, which is fixed (fixed output) and Adjustable (programmable / set). 
Examples are the AP1117 LDO regulator IC, LM317 and others. AP1117-ADJ is a type of adjustable're AP1117-3V3 is kind of fixed. 
Regulators LDO can also be made ​​from a combination of the FET with the TL431 as a regulator ic (latch), for example, is often found in computer PSU series as supply 3V3. So technically it can be said the contents of the above ic LM317 is a TL431 IC and an FET / TR type P. 
ability LDO regulator is also similar to the usual regulator, ie depending on the type of question. If the ability is only able to supply at 1A then only much alone ability, although there is input current of 10A. But the advantage is the wide input voltage fairly large when compared with the usual regulator. 
Figure 1117. When the LDO regulator output type fixed / fixed, then pin 1 earthed / gnd (image from another source)

Internal reference voltage LDO 1117 is 1V25, so when pin 1 (ADJ) digronkan, then serves as the LDO regulator with output 1V25. So it could be used to replace fixed 1117-1V2 LDO regulator output elusive.

Regulators DC to DC Converter

Regulator dc2dc created as a solution to cover the shortfall from the usual regulator and LDO regulator on top.Namely the limited current capability compared to the power input / output. 
With a range of DC to DC converter, to drop the voltage from 19V to 3V3, is able to supply up to 3A, while the LDO AP1117-33 just around 1,4A and 1A when to 7833. When using transistor could be bigger but not very effective. Or it could be said that DC 2 DC were able to maintain the power input, because it is very efficient, for example the input of 20V 1A (20W) can be easily lowered to 5V 3A (15W) can even be closer to the power input. 
The circuit power supply SMPS, is a DC to DC also, lowering the DC voltage into a DC voltage 300Van smaller. Likewise regulator, discussed here, how to work well together. No part of regulators pulse / frequency, error amp, and controls Protek (OVP / OCP etc). 
It generally consists of one IC controller which together with the final amplifier.For example SI-8001FFE (adjustable 0V8 s / d 24V input 3,5A s / d 40V, 300KHz), MC34063A (adjustable 2V s / d 24V 1.5A input 5 s / d 30V, 33KHz) and many more.
The main characteristic DC 2 DC circuit is the transformer / coil and controllers.Most designs DC to DC is adjustable (adjustable output voltage), but there is also a fixed / fixed. 
Examples of drawings and schematics dc2dc (from other sources)

Most of the supply panel / LCD TV screen, using dc2dc as a producer voltage, eg for voltage AVDD, DVDD IC COF. 
Defects in dc2dc among others:

1. The output voltage can not be locked because of damaged / changing the resistor value regulator output voltage (error amp).
2. Voltage does not come out, which may be caused by damaged circuit or IC controller fet / transistor final dc2dc damaged.
3. Protek. Usually characterized by output voltage keeps missing out briefly. Could be due oberload (OCP) or excess output voltage (OVP).

Replacing Regulator DC to DC Converter with Common Regulator / LDO

Is very imprecise and inefficient. Case in point: Desired regulator with 3A 20V input capability (60W) with an output of 5V 5A (power required 25W). When using IC 7805 (5V 1A) then the power of only 5W 7805, which would require a more current amplifier (1 or more TR in parallel) to be able to supply the power needed. So also when the LDO, limited in current output and thus require a current amplifier so it is not effective anymore