The difference between switch mode power supply and linear regulated power supply
What is a Switch Mode Power Supply?
The English name Switch Mode Power Supply, or SMPS for short, is a power supply unit (PSU) that uses some kind of switching device to transmit power from the source to the load. Normally it can be AC or DC, but the load is DC.
The most common application for a switch mode power supply is a power supply unit for a computer and has become the standard type of power supply for electronic equipment due to its high efficiency, low cost, and high power density.
Structural units
A switch mode power supply is a regulated power supply that uses a high frequency switching regulator to convert the power and regulate the output in an efficient manner.
A switching regulator is again a transistor (like a power MOSFET), just like a linear regulator, but the difference is that the pass transistor in an SMPS doesn't stay in saturation or fully on constantly, it's fully on Switching between a fully off state and a very high frequency, hence the name switch mode power supply.
Since the average time that the switching element (i.e. the transistor) is active is less, the amount of power that is wasted or dissipated as heat is very small compared to a linear regulated supply. This in turn leads to highly efficient operation of the SMPS because the voltage drop across the pass transistor (or switching element) is very small.
main advantage
Most electronic DC loads, such as microprocessors, microcontrollers, LEDs, transistors, chips, motors, etc., are powered from a standard power source such as a battery. Unfortunately, the main problem with batteries is when the voltage is too high or too low. Hence, the SMPS will provide a stable DC output.
SMPS is a multifunctional power supply, and different topologies can be selected according to the application type, such as boost, buck, input and output isolated power supplies.
In addition, a good SMPS design, its efficiency can be as high as 90% or even higher. In contrast, the efficiency of a linear regulated power supply depends on the voltage drop of the pass transistor, but in any case, its power supply efficiency is not as high as that of a switch-mode power supply.
What is power efficiency? As an example, suppose there is a 3V lithium battery that must be stepped down to a 1.8V load, consuming 100mA of current. The power wasted as heat in the transistor is 0.12W, so the power supply efficiency is 40%.
What's more, SMPS IC has more or less all the functions of discrete SMPS design, so it allows engineers to experiment with the design of custom projects.
