working of SMPS with neat block diagram.
asked Sep 3, 2019 in Power Electronics by
← Prev Question Next Question →
Advertisements

3 Answers

0 like 0 dislike


A block diagram of Switch Mode Power Supply is shown in figure. The first block is rectifier and filter that converts the A.C. supply voltage to pulsating D.C. which is then filtered out to reduce the amount of ripple content. This section uses the power diodes in bridge configuration to obtain the pulsating d.c. and the capacitor is used as a filter element. The second block is the high frequency switching section and it uses either MOSFETs or BJTs to convert the D.C. voltage to a high frequency ac\.c. square wave. This high frequency a.c. square waves ranges from 20 KHz to 100 KHz. Since the power transistors are not operated in their active region, their operation results in low power dissipation. Thus it is a two stage conversion i.e. the input a.c. supply voltage is first rectified to d.c. and then the high frequency switching section changes it back to A.C.


The next block of SMPS is high frequency power transformer that isolate the circuit and step up or step down the voltage to the desired voltage level. The output of the transformer is the input of the second rectifier section, called the output rectifier section. This rectifier section is different fron the first block of the rectifier in that the frequency of the voltage is very high. Therefore, the bridge configuration of this rectifier uses a high frequency diodes such as schottky diode and the output ripple is naturally filtered becouse of the number of the overlaps between each individual output pulse. Since the ripple is very small in output voltage of the rectifier, a small capacitance is required in the filter section


The last section of the SMPS is the control and feedback block, which contains circuitry that provides Pulse Width Modulation (PWM) output signal. The PWM controller provides duty cycle that varies pulse by pulse to provide an accurate d.c. output voltage. 

answered Sep 3, 2019 by
0 like 0 dislike

Working principle of SMPS: 

* SMPS converts unregulated AC or DC voltage into a regulated voltage.In case of AC it first converted into unregulated DC. This is fed to a high frequency switching element. The switch is operating at the high frequencies of 20 kHz to 1 MHz, chopping the d.c voltage into a high frequency square wave. This square wave is fed into power isolation transformer ,stepped down to a predetermined value and then rectified and filtered to produce the required d.c output.

* A portion of this output is monitored and compared against the fixed reference voltage and the error signal is used to control the on-off times of the swich, thus regulating the output.



answered May 21 by
0 like 0 dislike

Diagram: 



Working principle:- 

Rectifier and filter:- It converts the ac supply voltage to a pulsating dc, which is then filtered out to reduce the amount of ripple content. It uses the power diodes in a bridge configuration to obtain the pulsating dc and the capacitor is used as a filter element. 

High-frequency switching:- It uses either MOSFETs or BJTs to convert the dc voltage to high frequency ac square wave. This high-frequency ac square wave ranges from 20 kHz to 100 kHz. Since the power transistors are not operated in their active region, their operation results in low power dissipation. Thus, it is a two stage conversion. i.e. the input ac supply voltage is first rectified to dc and then the high frequency switching section changes it back to ac. 

High frequency power transformer:-It isolates the circuit and steps-up or steps-down the voltage to the desired voltage level. The output of the transformer is the input of the second rectifier section, called the output rectifier section. 

Output rectifier: - This rectifier section is different from the first block of the rectifier in that the frequency of the voltage is very high. Therefore, the bridge configuration of this rectifier uses a high frequency diode such as a Schottky diode and the output ripple is naturally filtered because of the number of overlaps between each individual output pulse. Since the ripple is very small in the output voltage of the rectifier, a small capacitance value is required in the filter section. 

Control and feedback:- It provides a pulse width modulation(PWM) output signal. The PWM controller provides a duty-cycle that varies pulse by pulse to provide an accurate dc output voltage.

answered Jun 5 by