hi ogu reginald
first of all , i will give u the overview of the inverter ,,
1) linear transformer based inverter
now i will tell u in detail about this type
-- LINEAR TRANSFORMER BASED INVERTER--
In this type of inverters ,,first of all 12vdc is converted into 12vac(square wave or modified sine wave or pure sine wave) now this 12vac is supplied to a step up iron core transformer ,which will give output around 220vac,,now the question arises that how much load u have to put on this 220vac ,,the answer is suppose your load is 500watts ,,so you have to chosse a stepup transformer of rating 12/220v 600VA..,,now again one question is arising in ur mind i.e. why 600VA? it is because in a simple alternating current (AC) circuit consisting of a source and a linear load, both the current and voltage are sinusoidal. If the load is purely resistive, the two quantities reverse their polarity at the same time. At every instant the product of voltage and current is positive, indicating that the direction of energy flow does not reverse. In this case, only active power is transferred.
If the loads are purely reactive, then the voltage and current are 90 degrees out of phase. For half of each cycle, the product of voltage and current is positive, but on the other half of the cycle, the product is negative, indicating that on average, exactly as much energy flows toward the load as flows back. There is no net energy flow over one cycle. In this case, only reactive energy flows—there is no net transfer of energy to the load.
Practical loads have resistance, inductance, and capacitance, so both active and reactive power will flow to loads. apparent power is the magnitude of the vector sum of active and reactive power. Apparent power is the product of the root-mean-square of voltage and current.
till now u have selected the required transformer for ur inverter, now we will do some calculations on measuring the transformer's input current so that u can make a power stage which will be capable of handling that much current
as we have selected a 600VA centertap(in our case ,u can select a 100VA also), as you are a beginner u can start with 100VA,,but u can also disagree with me.. now come on to the point ,,as we hve selected 600VA transformer so at full load the input current will be approx 600/12 i.e 50ampere .
now our aim is to make a power stage of inverter that can handle greater than 50 ampere(as a safe side) using MOSFETs.
now we have to drive these power mosfets using a driver circuit ,,this driver circuit will drive the mosfets in a pushpull topology,
if u want that ur output voltage should be constant i.e. does not decrease when the load is increased then you can also use a feedback network, let me clear you this in detail..suppose u hve made ur inverter which is giving 220vac at the output with no load, now when u connect a load (say 100 watt bulb) then the output voltage will not going to equal to 220v .it will be less than 220v ..but our aim is to keep the voltage constant at the output ..so there is need of some feedback network... now this feedback will control the dutycycle of the PWM signal which is driving the mosfets...suppose when there is no load then duty cycle is65% now as u connect the load ur duty cycle will increase say (80%) SO AS to keep the output voltage constant... i am giving u a circuit schematic
in the below figure u hve to replace the the power bjt TIP122 with power mosfet ,,.u can use irfz48n or irfz44n ,,just connect a small value(4.7 to 47 ohm) resistance between pin 11 and gate terminal ,,,,and also b/w pin 14 and gate terminal,,,, also put a 2k resistor b/w gate and source,, with source grounded...
if u want a simple schematic i.e without feedback then u can go with this schematic below
--BawA--