1KVA (1000 watts) Pure Sine Wave Inverter Circuit

A relatively simple 1000 watt pure sine wave inverter circuit is explained here.


As can be seen in the first diagram below, the configuration is a simple mosfet based designed for amplifying current at +/-60 volts such that the connected transformer corresponds to generate the required 1kva output.

Q1, Q2 forms the initial differential amplifier stage which appropriately raises the 1vpp sine signal at its input to a level which becomes suitable for initiating the driver stage made up of Q3, Q4, Q5.

This stage further raises the voltage such that it becomes sufficient for driving the mosfets.

The mosfets are also formed in the push pull format, which effectively shuffles the entire 60 volts across the transformer windings 50 times per second such that the output of the transformer generates the intended 1000 watts AC at the mains level.

Each pair is responsible for handling 100 watts of output, together all the 10 pairs dump 1000 watts into the transformer.
For acquiring the intended pure sine wave output, a suitable sine input is required which is fulfilled with the help of a simple sine wave generator circuit.

It is made up of a couple of opamps and a few other passive parts. It must be operated with voltages between 5 and 12. This voltage should be suitably derived from one of the batteries which are being incorporated for driving the inverter circuit.

The inverter is driven with voltages of +/-60 volts that amounts to 120 V DC.

This huge voltage level is obtained by putting 10 nos. of 12 volt batteries in series. 

The below given diagram shows a simple sine wave generator circuit which may be used for driving the above inverter circuit, however since the output from this generator is exponential by nature, might cause a lot of heating of the mosfets.
A better option would be to incorporate a PWM based circuit which would supply the above circuit with appropriately optimized PWM pulses equivalent to a standard sine signal.
The PWM circuit utilizing the IC555 has also been referred in the next diagram, which may be used for triggering the above 1000 watt inverter circuit.

Parts List

All resistors are 1/8 watts, 1%, MFR
R1 = 14K3 (12K1 for 60Hz),
R2, R3, R4, R7, R8 = 1K,
R5, R6 = 2K2 (1K9 for 60Hz),
R9 = 20K
C1, C2 = 1µF, TANT.
C3 = 2µF, TANT (TWO 1µF IN PARALLEL)
C4, C6, C7 = 2µ2/25V,
C5 = 100µ/50v,
C8 = 22µF/25V
A1, A2 = TL 072

Part List for Inverter

Q1, Q2 = BC556

Q3 = BD140

Q4, Q5 = BD139

All N-channel mosfet are = K1058

All P-channel mosfets are = J162

Transformer = 0-60V/1000 watts/output 110/220volts 50Hz/60Hz


The proposed 1 kva inverter discussed in the above sections can be much streamlined and reduced in size as given in the following design:

The diagram also shows the method of connecting the battery, and the supply connections for the sine wave or the PWM oscillator stages.

Here just four mosfets have been used which could be IRF4905 for the p-channel, and IRF2907 for n-channel. 

Complete 1 kva inverter circuit design with 50 Hz sine oscillator