SMPS | Circuit Diagram | principal of operation of SMPS

 

SWITCHING MODE POWER SUPPLY

SMPS or Switching mode power supply is an Electronic device which

supply power from a DC or AC source to DC loads. SMPS convert

Electrical Power supply by using Switching Regulator. 

lets discuss more about SMPS given bellow. before discuss the SMPS we

have to know what is the Regulated Power Supply.

What is Regulated Power Supply

A DC power supply which maintain a constant output voltage irrespectively

changing ac line or varying load current is known as Regulated Power

Supply.

Classification of regulated power supply

        i.          Zener diode voltage regulator.

      ii.          Linear regulator.

    iii.          Switched regulator.

 Classification of Switched regulated power supply

                                              i.          PWM Switched mode

                                            ii.          Resonant switched mode

Classification of PWM Switched mode

      i.       Boost converter

    ii.          Buck converter

  iii.          Buck-Boost converter

  iv.          Cuk converter.

 
 

 

Principal of operation of SMPS

In an SMPS, The AC supply from the mains is first applied to a rectifier circuit & filter which convert the AC supply into a very high filtered dc voltage. This high voltage supply is then given to switching transistor circuit. The switching transistor circuit switched ON & OFF at a very HIGH speed by pulse width modulator which generate high frequency square pulses (typically 20 KHz to 50 KHz). The switching transistor switch the high volt DC ON and OFF at the same frequency to result in the square pulse at its output.

The square pulse are the given to the primary winding of transformer. These pulses induce a voltage in the primary winding of transformer, which in trans generates a voltage in the secondary winding. The RMS value depends on the ON-OFF ratio of the switching circuit. Due to high frequency involved, a small ferrite core transformer having low power loss can be used.

The voltage at secondary winding is the rectified and filter to produce the output.

To regulated the output voltage Vout, a part of rectified output as generate above its feedback to the switching circuit through resistive attenuator circuit. The feedback voltage is applied to an error amplifier which compare it to a reference voltage and generates an error voltage. The error voltage is amplified and used to control ON-OFF ratio of PWM. The output voltage from the PWM controls the action of Switching circuit.

Hence, the ON-OFF ratio of the PWM controls the rms voltage to the primary winding, resisting in regulating the final DC output.

 

Advantages of SMPS:

·      High Efficiency

·      Low heat generates

·      Boost or Buck or Negative operation

Disadvantage of SMPS:

·      More external port required

·      Complicated design

·      Increased noise

 

 

Advantages & Disadvantage of Linear Power Supply:

         Advantages:

·      Simple circuit configuration

·      Few external port not required

·      Low noise

 

Disadvantages:

·      Relatively poor efficiency

·      Considerable heat generation

·      Only step down (buck operation)

 

You can Also read: What is UPS

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