Your Guide on Switched Mode Power Supply
Updated: Aug 5, 2020
A switch-mode power supply (SMPS) is a type of power supply that uses semiconductor switching techniques, instead of standard linear methods to provide the required output voltage. It converts power by switching devices that turn on/off at high-frequencies or with the help of inductors or capacitors to supply power when the switching device is in a non- conductive state. They can be found in most PC’s, power amplifiers, TV’s, dc motor drives, etc.
TYPES OF SMPS
The power received from the AC main is resolved and filtered as high voltage DC. Then, it is switched and fed to the main side of the step-down transformer. This transformer is smaller than a 50 Hz unit, thus releasing the size and weight problems. The filtered and rectified output is collected at the minor side of the transformer, which is then sent to the o/p of the power supply.
In a forward converter, the choke transmits the current whether the transistor is conducting or not. The diode transmits the current through the OFF period of the transistor to support the energy flow through the load. The choke stores energy during the ON period and also permits some energy into the output load.
In this converter, the magnetic field of the inductor supplies the energy throughout the ON period of the switch. The energy is emptied into the output voltage circuit when the button is in the open state. The duty cycle controls the output voltage in a flyback converter.
Self-Oscillating Flyback Converter
This is the simplest converter based on the principle of the flyback. During conduction, a current through the transformer primary starts to ramp up linearly with the slope Vin/Lp. The induced voltage in the secondary winding and the feedback winding make the fastest recovery rectifier reverse biased and hold the conducting transistor ON. The core begins to saturate once the current reaches its peak value, the current inclines to increase very sharply. This cannot be supported by the fixed base drive supported by the feedback winding. As a result, the switching activates to come out of saturation.
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