SMPS is basically a highly efficient power supply unit that incorporates a switching regulator.In all power supply units there will be a regulator section for maintaining the desired output levels. In ordinary linear regulator there will be transistor operating in active mode.Here desired output is maintained by dissipating power in power transistors. So when ever the device is on it will be consuming power.So due to these reasons there is a huge power losses. Hence their maximum efficiency is only 50%.But switched-mode power supply regulates either output voltage or current by switching ideal storage elements, like inductors and capacitors into and out of different electrical configurations.Here a transistor is switched between active mode and cut off mode. A pulse width modulated wave is used for this switching. A block diagram is shown below.
Input to the SMPS is the AC power supply. Initially it is full wave rectified and then filtered to obtain a DC waveform. It is then send to a chopper section where this DC wave is chopped to get a high frequency wave. Usually the frequency of the chopped wave is kept above 20kHz to make it inaudible for humans. It is then fed to to the output transformer to transform the voltage levels of desired range. Here the transformer size is very small since the operating frequency is very high. A transformer's power handling capacity of given size and weight increases with frequency provided that hysteresis losses can be kept down. Therefore, higher operating frequency means either higher capacity or smaller transformer.This is why SMPS is of small size when compared with ordinary power supplies which operate at low power supply.The output of this transformer is fed to the output rectifier and filter stage in order to convert it again to DC. The output is fed back to chopper via chopper controller. Chopper controller senses the variations in the load and adjust the duty cycle of the chopping pulse . As the duty cycle increases the power delivered increases.
This method draws only the power required by the load. In all SMPS topologies, the transistors are always switched fully on or fully off.Thus the efficiency is very high (around 90-95%). This method also gives better regulation.Since small transistors are used heat generated is also very less.Due to these advantages these are widely used for PC power supplies,Mobile Phone chargers and many more.
Input to the SMPS is the AC power supply. Initially it is full wave rectified and then filtered to obtain a DC waveform. It is then send to a chopper section where this DC wave is chopped to get a high frequency wave. Usually the frequency of the chopped wave is kept above 20kHz to make it inaudible for humans. It is then fed to to the output transformer to transform the voltage levels of desired range. Here the transformer size is very small since the operating frequency is very high. A transformer's power handling capacity of given size and weight increases with frequency provided that hysteresis losses can be kept down. Therefore, higher operating frequency means either higher capacity or smaller transformer.This is why SMPS is of small size when compared with ordinary power supplies which operate at low power supply.The output of this transformer is fed to the output rectifier and filter stage in order to convert it again to DC. The output is fed back to chopper via chopper controller. Chopper controller senses the variations in the load and adjust the duty cycle of the chopping pulse . As the duty cycle increases the power delivered increases.This method draws only the power required by the load. In all SMPS topologies, the transistors are always switched fully on or fully off.Thus the efficiency is very high (around 90-95%). This method also gives better regulation.Since small transistors are used heat generated is also very less.Due to these advantages these are widely used for PC power supplies,Mobile Phone chargers and many more.
1 comments:
Informative post regarding the functionality of a SMPS. Basically a SMPS works to regulator section for maintaining the desired output levels. This is the main function of SMPS. Thanks for sharing the useful read.
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