DC-AC Inverter By: Dave Kresock 4/24/08

Original Design That I Found The op-amp and the and gate work together to assure the TX1 and TX2 are not on at the same time. Optoisolators are used to isolate the logic side from the power side

Inverter Concept Diagram Inverter Control Circuit Transformer To Transformer120 Vac Out In From 12 Vdc Source

Original Circuit Logic SidePower Side

Circuit Component Functions Logic Side  The 555 timer, along with R3, R4, and C1 are designed to provide the J-k flip-flop with a 120 Hz frequency based on the following equation: f = 1.44/[(R3+R4)*C1] Therefore: R3 = [1.44/(f*C1)] = R4 Using a 1kΩ resistor for R4: R3 = [1.44/(120*1µ)] – 1000 = 11,000Ω  Since the inverter will be powered from a 12 Vdc source, Inductor L1 is needed as a buffer between the battery and the supply pins of the ICs.  The J-K flip-flop provides the precise 50% duty cycle that will be applied to turn on each transistor at alternating frequency of 60 Hz.

Circuit Component Functions Power Side  Transistors Q1 and Q2 determine how much wattage the inverter can supply. This inverter is designed for approximately 100W.  Diodes D1 and D2 protect the transistors when they turn off and the magnetic field collapses. This is a safe way to dissipate the energy stored in the inductance of the primary winding.

Waveforms Channel 1 (Blue) = Output of the Q-pin of Flip-Flop Channel 2 (Red) = Output of the Q/-pin of Flip-Flop Note the alternating waveforms and 50 % duty cycle.

Waveforms Channel 1 (Blue) = TX1 Drain Channel 2 (Red) = TX2 Drain This is an area for concern. As TX1 turns on, it’s instantaneous. However, as TX2 turns off, it’s much slower.

Waveforms Channel 1 (Blue) = TX1 Drain Channel 2 (Red) = TX2 Drain With both transistors on for 200µS, (2.5%), the current is doubled

Waveforms Channel 1 (Blue) = Output of the Q-pin of Flip-Flop Channel 2 (Red) = Output of the Transformer Transformer Output: Hz

Unnecessary Components

Let there be light!