How to Build a Homemade Pure Sine Wave Inverter, Using IC 555Posted by hitman The proposed circuit generates accurately spaced PWM pulses which imitates a sine wave very closely and thus can be considered as good as its sine wave counter part design. Here we use two stages for creating the required PWM pulses, the stage comprising the ICs 741 and the other comprising the IC 555. Let’s learn the whole concept in details. How the Circuit Functions – The PWM Stage The circuit diagram can be understood with the following points: The two op amps are basically arranged to generate the required sample source voltages for the IC 555. The couple of outputs from this stage is responsible for the generation of square waves and triangular waves. The second stage which is actually the heart of the circuit consists of the IC 555. Here the IC is wired in a monostable mode with the square waves from the op amp stage applied to its trigger pin #2 and the triangular waves applied to its control voltage pin # 5. The square wave input triggers the monostable to generate a chain of pulses at the output where as the triangular signal modulates the width of this output square wave pulses. The output from the IC 555 now follows the “instructions” from the op amp stage and optimizes its output in response to the two input signals, producing the sine equivalent PWM pulses. Now it’s just a matter of appropriately feeding the PWM pulses to the output stages of an inverter consisting of the output devices. The other two transistors make sure that the conduction of T1 and T2 takes place in tandem that is alternately so that the output o from the transformer generates one complete AC cycle with the two halves of the PWM pulses. the transformer and the battery. The Output Stage The above PWM output is applied to the output stage as shown in the figure. Transistors T1 and T2 receive the PWM pulses at their bases and switch the battery voltage into the transformer winding according to the duty cycles of the PWM optimized waveform. . R12. R13 = 33 Ohms 5 Watt. R16 = 1K. R6 = 1K5 C1 = 0. T3. T5. R9. R8. R11. IC2 = 555. R15. T1. T2 = BDY29. C2 = 100 pF. T6 = TIP 127.Parts List R1.1 uF. R10 = 10K. . 100 AH. IC1 = TL 072. R14. 200 Watts. R7 = 8K2. R4 = 1M preset. Battery = 12 volts. R3. R2. R5 = 150 K preset. T4 = TIP122 Transformer = 12 – 0 – 12 V. via the corresponding diodes. The 24 batteries need to be made out of two 12V 40 AH batteries in series. which requires lowest number of components and yet is able to produce optimum results. here it has been dimensioned for generating around 50 Hz output. The circuit has been exclusively developed and designed by me. The supply to the ICs must be provided from any of the batteries. N5) Until here. The IC 555 section has been wired up as an astable MV. From the circuit diagram we are able to witness the many obvious stages of an inverter topology. however it's the digital version and is almost as efficient as its sinusoidal counterpart. The MOSFETs used may be any type able to handle 50V at 30 amps. the 100K pot is used for optimizing the PWM effect from pin#3 of the IC. The 100K pot should be adjusted using an RMS meter for making the RMS value at the output as close as possible to an original sine wave signal at the relevant voltage. . The circuit was requested by one of the active participants of this blog. the stages behave as an ordinary square wave inverter. The gates are from the IC 4049 which consists of 6 NOT gates. two have been used in the oscillator stage while the remaining four are configured as buffers and inverters (for flipping the square wave pulses. The circuit is not actually a sine wave in true sense.Make 400 watt MOSFET Sine Wave Inverter Circuit Posted by Swagatam The post explains probably the most easiest 400 watt sine wave inverter circuit. The gates N1 and N2 form the oscillator stage and is responsible for generating the basic 50 or 60 Hz pulses. N4. because the ICs will get damaged at 24Volts. The negative going pulses from the IC 555 are only utilized here for trimming the square wave pulses at the gates of the respective MOSFETs. but the introduction of the IC 555 stage transforms the entire configuration into a digitally controlled sine wave inverter circuit. . of 12 volt batteries in series. 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. 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. As can be seen in the first diagram below. This voltage should be suitably derived from one of the batteries which are being incorporated for driving the inverter circuit. It is made up of a couple of opamps and a few other passive parts. This huge voltage level is obtained by putting 10 nos. It must be operated with voltages between 5 and 12. together all the 10 pairs dump 1000 watts into the transformer. Q5. a suitable sine input is required which is fulfilled with the help of a simple sine wave generator circuit.Make This 1KVA (1000 watts) Pure Sine Wave Inverter Circuit Posted by hitman A relatively simple 1000 watt pure sine wave inverter circuit is explained here. 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. Each pair is responsible for handling 100 watts of output. For acquiring the intended pure sine wave output. The inverter is driven with voltages of +/-60 volts that amounts to 120 V DC. . which may be used for triggering the above 1000 watt inverter circuit. however since the output from this generator is exponential by nature. might cause a lot of heating of the mosfets. The PWM circuit utilizing the IC555 has also been referred in the next diagram.The below given diagram shows a simple sine wave generator circuit which may be used for driving the above inverter circuit. 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. . R5. R6 = 2K2 (1K9 for 60Hz). R8 = 1K. C3 = 2µF. A2 = TL 072 Part List for Inverter Q1. C8 = 22µF/25V A1. C6. R2. C7 = 2µ2/25V. TANT (TWO 1µF IN PARALLEL) C4. R7. C2 = 1µF. C5 = 100µ/50v. 1%. MFR R1 = 14K3 (12K1 for 60Hz). R3. R4. Q2 = BC556 Q3 = BD140 Q4.Parts List for the sine generator circuit All resistors are 1/8 watts. TANT. Q5 = BD139 All N-channel mosfet are = K1058 All P-channel mosfets are = J162 Transformer = 60-0-60V/1000 watts/output 110/220volts 50Hz/60Hz . R9 = 20K C1. High Efficiency Sine Wave Inverter .Part 3 (Inverter Board) To recap a little bit Ill briefly explain how the sine wave inverter works. There is an on-board sine wave generator that is used as the input signal to the “amplifier”. the amplified input signal generated by the on-board oscillator remains. If you need further and more detailed explanation please read the first article of this series HERE. Here is the schematic for the oscillator that generates the input signal: This is simply a quadrature oscillator. Then another op-amp is configured as an unity gain amplifier to act as a buffer so that the following steps don't deform the generated sine wave. The active filter should have a cut-off frequency just a little above of the desired output frequency. The first op-amp generates a square wave of the required output frequency (in this case 50Hz or 60Hz). The inverter creates a square wave suitable for MOSFET switching with minimal power loss as heat because the MOSFETs will not be in the linear region. Basically this inverter is a Class D audio power amplifier designed to work with high voltages. . After filtering out the high frequency square wave. This square wave is then filtered of all its harmonics making it a beautiful sine wave by the second op-amp that is configured as an active low pass filter. I will not discuss in detail how this is accomplished. One of the properties of the capacitors is that voltage can not change abruptly.uk/pwm.html . The generated ramp is fed to a comparator as well as the sine wave generated by previous block. When the voltage of the ramp is greater than the voltage of the sine (reference voltage) it generates a perfectly square pulse lasting until the voltage of the ramp drop below the sine voltage. NOTE: This image is property of: http://www. The schematics of the ramp generator is illustrated above.cpemma. in this case 20kHz). Now.co. there are numerous 555 timer tutorials in the internet.To implement the PWM (pulse width modulation) circuit a ramp generator was used in conjunction with an op-amp configured as a comparator. here is where the magic takes place. Since we are charging it at constant current the voltage across the capacitor increases linearly. The 555 timer controls the time that the capacitor is going to be charged (it sets the PWM frequency. The 555 is operated with a current limiter to charge a capacitor at constant current. If both wires (power output of the inverter) are in phase then the voltages will be the same thus no current would be able to flow. When there is a voltage too high it conducts infinite amount of current (reverse biased) to ground.1uF@1000V capacitor from the positive rail to ground. This capacitor absorbs large spikes and if any voltage remains above desired limits the TVSs take care of it by dissipating it as heat. This chip squares up the wave even better and it also generates a wave that is 180 degrees out of phase. TVS diodes work as zener diodes. The IR21834 chip handles this by making a “fake ground” at the high side MOSFET's Source pin.In the illustration all the pulses are of equal length because the reference signal is a constant voltage but in the circuit the pulses will be of different length because the reference is a sine wave (variable voltage). The only difference is that one side takes care of the original signal and the other side deals with the signal that have been shifted by 180 degrees. Then. . Spike filtering is done with TVS diodes (transient voltage suppressor diodes) across each MOSFET and a very famous 0. When this happens both MOSFETs are conducting thus creating a short to ground. This makes possible current flow in the output. the gate is driven by a higher voltage to ensure that the MOSFET is fully on when a pulse from the signal comes. Now I think that this is the most important part of the circuit. There are two half bridge drivers in this circuit and they essentially do the same task. The output signal is then fed to a 4011 CMOS NAND gate. the two half bridge drivers. It is necessary to use a H bridge driver because the MOSFETs that are connected to the positive rail have their Source pin “floating” and thus they can not be fully turned off creating a very serious condition in the half bridge. it is just two coils and one capacitor connected across the output of each half bridge. The output from the MOSFETs is the power output. The filter is very simple. Zener diodes are used in the gates too in case that there is a spike that exceeds the Gate to Source voltage of the MOSFETs. This zener should dissipate that spike by clamping it. An illustration is shown below.6 Ohm resistor with a diode across it to avoid ringing.As in any other driving circuit. Efficiency tests will be posted shortly. Click the image for the full schematic of the inverter board: . All MOSFETs have a 5. care must be taken about ringing. now all thats left is to filter the high frequency out and stay with the amplified sine wave. I used a 1k Ohm resistor from Gate to Source to make sure that the MOSFET's internal parasitic capacitor discharges entirely before the next pulse comes by. . It shows the output before and after filtering. .As a bonus here is a picture that I took of the oscilloscope's screen. This information is provided AS IS. The use of this information for commercial purposes without my authorization is a violation to copyrighted material and will be prosecuted by law. Without them this project would have been impossible. The owner of this material.I want to give special thanks to Don Carroll and to Ross Wheeler for helping me out so much with this project. all pictures shown here and all schematics are copyrighted material. Argenis Bilbao (myself) prohibit the use of this information for anything other than personal use or educational purposes. WARNING: This information. EXTREMELY High voltages are used in this project so extreme caution must be used while handling any electronics. I am not to be held responsible for any damages caused to you or others by the use of this information. .
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