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What is The SMPS?

Switch Mode Power Supply or SMPS is a type of Power Supply Unit (PSU) that uses some kind of switching devices to transfer electrical energy from a source to load. Usually, the source is either AC or DC and the load is DC.

Old Computer SMPS(source)

SMPS is a type of regulated power supply that uses a high-frequency switching regulator to convert the power supply and also regulate the output in a highly efficient way.

SMPS Working Principle

A switching regulator does the regulation in the SMPS. A series switching element turns the current supply to a smoothing capacitor on and off. The voltage on the capacitor controls the time the series element is turned. The continuous switching of the capacitor maintains the voltage at the required level.

Why is Name Switching Mode Power Supply? 

The switching regulator is again a transistor(MOSFET), just like in Linear Regulator but the difference is that the pass transistor in SMPS doesn’t continuously stay in saturation or fully ON state but rather switches between fully ON and fully OFF states at a very high frequency. Hence the name Switching Mode Power Supply.

Since the average time the switching element i.e. the transistor stays in the active state is less, the amount of power wasted or dissipated as heat is very less when compared to Linear Regulators. This, in turn, leads to a high efficiency of SMPS as the voltage drop across the pass transistor (switching element) is very less.

Switching Action

The switching action of the transistor is controlled using a technique called Pulse Width Modulation (PWM) and the output voltage can be regulated by the duty cycle of the PWM.

Diagram Of SMPS Unit
SMPS Circuit Diagram

In this, the unregulated DC supply is given to a Switched Mode DC – to – DC Chopper Circuit and the output is a regulated DC Supply.

Application Of SMPS

The most common application of an SMPS is the power supply unit of a computer. Switching Mode Power Supply (SMPS) has become a standard type of power supply unit for electronic devices because of their high efficiency, low cost, and high power density.

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