SMPS component and TL494

For introduction of SMPS : 
http://articleelectrical.blogspot.in/2018/02/switched-mode-power-supply-smps.html

TRANSFORMER

A single-phase voltage transformer generally comprises of two electrical coils of wire, into that constructive part one called the “Primary Winding” and another called the “Secondary Winding”. The “primary” side of the transformer as the side that normally takes power and the “secondary” as the side that normally delivers power. In a single-Phase voltage transformer, the primary side with the higher voltage and the secondary side is stepped down the primary voltage

             FIG. High frequency and Multi-secondary transformer

RECTIFIER BRIDGE

l  To transform a AC into DC there are four diodes make configuration which is called a bridge rectifier. The diodes in the bridge circuit supply the same polarity of output for either polarity of input. 

l  Bridge rectifiers are used for converting the alternating current (A.C.) into direct current (D.C.) to use of colloquial appliances. When power comes in through the power lines, the transformer drops it to about 110V to about 3-24V after which, the rectifier converts the current. The bridge rectifier is situated between the capacitors and Transformers.

l  A bridge rectifier is used for converting AC to DC. Cell phones and personal digital assistants (PDA) use AC adapters. Bridge rectifiers are AC adapters

      FIG Bridge Rectifier and symbol

  

CAPACITOR

l  Capacitor is an electronic ingredient that stores electric charge . Capacitor is made by 2 plates which is particularly separated by Dielectric material.

l  One plate compile Positive(+ve) charge and the other plate compile Negative(-ve) charge.

               FIG TYPICAL CAPACITOR                                     FIG CONSTRUCTION OF CAPACITOR 

There are simple form of the capacitor is usually as parallel plate capacitor .it is made up with the two metallaised foil plates at a distance parallel to each other and value of that capacitance in Farads. , being fixed by the surface area of the conductive plates and the distance of separation between them. Altering any two of these values alters the the value of its capacitance and this forms the basis of operation of the variable capacitors.

Design Equation

       TABLE: Design Equation relation

Pin Configuration and Functions of TL494 

                           

          FIG : IC TL494 Pin configuration and Pin connection

TL494 Features

Ø  Output Control Selects Single-Ended or Push-Pull Operation

Ø  Internal Circuitry Prohibits Double Pulse at Either Output

Ø  Variable Dead Time Provides Control Over Total Range

Ø  Internal Regulator Provides a Stable 5-V Reference Supply With 5% Tolerance

Ø  Circuit Architecture Allows Easy Synchronization

Ø  Uncommitted Outputs for 200-mA Sink or Source Current

Principle Of Operation

u  The TL494 is a fixed-frequency pulse-width-modulation (PWM) control circuit.

u  Modulation of output pulses is accomplished by comparing the sawtooth waveform created by the internal oscillator on the timing capacitor (CT) to either of two control signals.

u   The output stage is enabled during the time when the sawtooth voltage is greater than the voltage control signals.

u  As the control signal increases, the time during which the sawtooth input is greater decreases; therefore, the output pulse duration decreases.

u  A pulse-steering flip-flop alternately directs the modulated pulse to each of the two output transistors.

u  Figure shows the relationship between the pulses and the signals.

u  The control signals are derived from two sources: the dead-time (off-time) control circuit and the error amplifier.

Applications Of  IC TL494

Ø  Desktop PCs

Ø  Microwave Ovens

Ø  Power Supplies : AC/DC

Ø  Solar Micro Inverter

Ø  Smoke Detector

Ø  Solar Power Inverter