Switch Mode Power Supply and its Types

Switch mode power supplies are widely used because of the advantages they provide in terms of weight, size, efficiency, cost, and overall performance. They have increasingly become an accepted part of the electronics scene, and they are often referred to as switch mode power converters, or simply switches.

What is SMPS?

Switched Mode Power Supply or SMPS is an electronic circuit that converts power either by using switching devices that turn on/off at high-frequencies or with the help of capacitors or inductors to supply power when the switching device is in non- conduction state.

Switched Mode Power Supply is widely used in electronic equipment, namely computers and several other devices that require an efficient and stable power supply. Besides its overall performance, SMPS have plenty of advantages that range from its size, weight, cost, to efficiency.

In simple words, SMPS circuit converts and regulates the energy with power semiconductors that are switched on/off with high-frequency.

Types of SMPS

DC-DC Converter

In this, the power received from AC mains is rectified and then filtered as a high-voltage DC. This high voltage DC is then switched and fed to the step-down transformer on the primary side. On the secondary side of the step-down transformer, the rectified & filtered output is collected, and then it is ultimately sent as the output to the power supply.

Forward Converter

Irrespective of whether the transistor is conducting or not, the choke carries the current in the forward converter. During the OFF period, the diode inside the transistor carries the current to support the energy flow through the load. During the ON period, the choke stores the energy and also passes a part of that energy to the output load.

Flyback Converter

In this converter, during the ON period of the switch, the magnetic field of the inductor stores the energy. When the switch is in open state, then the energy is emptied into the output voltage circuit. The Duty cycle here in the Flyback converter is determined by the output voltage.

Self-Oscillating Flyback Converter

This converter is based on the Flyback principle. During conduction, a current through the transformer primary starts ramping up linearly with the slope Vin/Lp. Since the voltage is induced in the feedback winding and the secondary winding, the fast recovery rectifier starts operating in reverse biased and holds the conducting transistor ON. The core starts saturating once the current reaches its peak value. This result in a sharp rise in current that is not supported by the fixed base drive further supported by feedback windings. Hence, the switching starts coming out of saturation.

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