Switch Mode Power Supply (SMPS)

Switch mode power supplies(SMPS) are an extraordinary array of high frequency alternative. These are the Switching Regulators offers higher efficiency then liner regulators. In addition the Power Supply SMPS can step-up, down and invert the input voltage.

Working principal of Switch Mode Power Supply
A switching regulator is a circuit that uses an inductor, a tranformer, and a capacitor as energy-storage element to tranfer energy from input to output in discrete packets. Feedback circuitry regulates the energy tranfer to maintain a canstant voltage within the load limits of the circuit.
They use some form of pulse-width modulation to alter the on time relative to the off time to effect control. The device used in this to giveen the constraints of frequency and the speed are power ?fets?
The use of power ?fets? with fast turn-on and turn-off characteristics have made switches that operate comfortable at frequency above 100khz practical.
There are two topologies are used

• Forward converters
• Flyback circuits.

Forward converters are used in medium and high power applications. They can be recognizeed by their power transformer and output choke.
Flybacks are favored for low power applications because they employ a transformer that doubles as the input choke
Using a transformer as the energy-storage element also allows output voltage to be electrically isolated from the input voltage.

Advantages of Switch Mode Power Supply

• Change the output to a different voltage level then the input ( step-up or step-down).
• Isolate the output from the input.
• Provide the user with a means to vary the output
• Can get constant output at variable input.
• Stabilize the output against the influence of:-
  • Source changes (source effect)
  • Load changes (load effect)
  • Temperature changes ( temp. Effect)
  • The passage of time ( time effect or drift)
• Output short circuit protected.

Applications of Switch Mode Power Supply
SMPSs are having wide range of applications some of them are -

• Machine tool industries
• Security systems (Close Circuit Cameras)
• Where the size and wight very less is required
• Audio and vedio application
• Support supplies with PLC?s

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