50W 12V to 220V DC-AC Converter

Figure 1 

The circuit is aimed to produce a 50W power converter that would supply different small appliances by converting 12 VDC to 220 VAC, and the process is known as inverter.

• 4060 – a 14-bit ripple counter with internal oscillator that has glitches which may occur in any logic gate systems connected to its outputs due to the slight delay before the later counter outputs respond to a clock pulse
• 4013 – a dual type D flip flop constructed with MOS P-channel and N-channel enhancement mode device in a single monolithic structure with features such as single supply operation, diode protection on all inputs, noise immunity, toggle rate of 4 MHz at 5 Vdc, designed with logic edge clocked flip flop, quiescent current of 2 nA at 5 Vdc, and static operation
• 4047 – a multivibrator capable of operating in either monostable or astable mode having features like asynchronous master reset, retriggerable option available for pulse width expansion, enabled with either a low or a high level in the astable mode, true and complementary buffered outputs, and output pulse width independent of the trigger pulse
• BD139 – NPN power transistor used for driver stages in hi-fi amplifiers and television circuits because of its low voltage at 80 V maximum and high current at 1.5 A maximum

One of the main components that comprise the circuit consists of an oscillator that is built in the region of IC1, which is made of crystal providing mechanical resonance to create an electrical signal with a very precise frequency. The simple crystal CR1 provides excellent reference frequency at 50 Hz. The frequency of oscillation, precisely 204.8 KHz at point P1, is being regulated by the parallel combination of capacitor C1 and variable capacitor Cx. Another component is the monostable/astable multivibrator IC3 which gives the symmetrical output of a square wave signal with 50 Hz frequency. This process will be followed by a buffer stage using FET Q1 & Q2 with Q3 & Q4 as the driving stages while a heatsink is placed in the power transistors using Q5 & Q6 with Q3 & Q4 as the power stage.

The power transistors are being protected by Zener diodes D2 & D3 from voltage peaks produced by the transformer T1. The transformer is connected to the CO1 contacts for halfway reception. It is connected in reverse where the secondary coil becomes the primary and the halfway reception is connected to the positive pole of the battery while the other two contacts to the Q5 & Q6 emitters. These transistors are grounded alternately depending on the pin 10 and pin 11 output of IC3. Doing this will allow AC to flow in the primary with 220 VAC square wave runs on the secondary. The output voltage at no load is larger than the voltage with load. Same thing applies to the amount of voltage supplied by a battery source.

Figure 2 

The DC to AC inverters are widely used in rural electrification the require AC power which includes solar home systems, health clinics, and community centers. They can also be used for other photovoltaic systems that convert light energy into electricity such as weekend homes and remote cabins, boats and caravans, and small telecom photovoltaic systems.

Source:users.otenet.gr/~athsam/12vdc_to_220vac_converter.htm