Generating spwm using a 555 timer and 8038

[princeguru]

Generating spwm using 555 timer and 8038

hi everyone!
please i a kind of new in this please i want to ask this
i want to generate spwm to drive my mosfet gate for inverter though I'm not using programming i want to do this using 555timer to generate my triangular wave[16khz] and 8038 to generate my sinewave[50hz] at different frequency i will then feed these two output to the input of an omp-amp in order to generate spwm
Please i want to ask is this method a good one please your advice is seriously needed

 

[BradtheRad]

Re: Generating spwm using 555 timer and 8038

Below is link to recent similar discussion about the 8038 IC.
Radio Shack once carried it but I have not seen any more available after I destroyed mine years ago.

https://www.edaboard.com/showthread.php?t=374566

 

[BradtheRad]

Re: Generating spwm using 555 timer and 8038

Are you satisfied with an approximation of a sinewave? Then you can arrange a 555 IC to generate the SPWM. Duty cycle is changed by varying voltage on the 'ctl' pin. By applying a sinewave you obtain SPWM at the output. The signal should come through a low resistance so that it is a chief influence on the timing behavior in the IC. You must experiment with your 555 IC, to discover what voltage to apply at the ctl pin, to get a particular duty cycle.

The 50 Hz square wave (DC pulses) at left can come from a second 555, or a pulse generator of your choice. Filter it through an RC network. My simulation below has 2 capacitors and a potentiometer, as a dubious attempt to shape the waveform so it is more sine-like.

 

[princeguru]

Re: Generating spwm using 555 timer and 8038

thank you so much BradtheRed for your advice but if i may ask what will be the frequency at pin3 i.e the out3 and can it be use to drive my mosfet

 

[BradtheRad]

Re: Generating spwm using 555 timer and 8038

thank you so much BradtheRed for your advice but if i may ask what will be the frequency at pin3 i.e the out3 and can it be use to drive my mosfet

Close to 1 kHz. Most builders use a higher carrier frequency, so that a circuit can use smaller value inductors. I only used a low carrier frequency to allow the scope traces to show all waveforms individually and clearly.

My simulation makes a waveform that can drive an NPN or N-mos. However it is common for an inverter to have more than one switching device. Each device needs its particular waveform. It might be an inversion of my waveform, or it might be negative polarity, etc.

 

[princeguru]

Re: Generating spwm using 555 timer and 8038

ok can i use in conjunction with sg3525 so that the sg will generate my 50hz because it's for inverter i'm designing it i'm trying to see if iw can design sinewave inverter without programming. u made mention of some inverter having more than one switching devices i don't understand that please can u elaborate on that

 

[princeguru]

Re: Generating spwm using 555 timer and 8038

let me ask what if i use two different 8038 one for 50hz and the other for triangular i.e the carrier wont it work

 

[Audioguru]

Re: Generating spwm using 555 timer and 8038

An inverter has an AC output using push-pull output devices. You were talking about using only one Mosfet for switching then it will not produce AC, instead it will produce a pulsing DC.
You can use two obsolete ICM8038 ICs or any triangle and sinewave circuits.
Electricity is reliable here so I have never used an inverter or a SG3525. Doesn't a SG3525 generate its own PWM that you modulate with your 50Hz sinewave?

 

[princeguru]

Re: Generating spwm using 555 timer and 8038

An inverter has an AC output using push-pull output devices. You were talking about using only one Mosfet for switching then it will not produce AC, instead it will produce a pulsing DC.
You can use two obsolete ICM8038 ICs or any triangle and sinewave circuits.
Electricity is reliable here so I have never used an inverter or a SG3525. Doesn't a SG3525 generate its own PWM that you modulate with your 50Hz sinewave?

yes sg3525 or sg3524 regulated pwm but it can not be use for sinewave and if you try filtering it with LC filter you will not like the out because i have experiment it so i know what I'm talking. My aim is to design an inverter with pure sinewave output that is why I'm looking at driving my switching unit using spwm so that after filtering with Lc filter i will have a sinewave hope you get me now

 

[Audioguru]

Re: Generating spwm using 555 timer and 8038

The SG3525 regulates its output voltage with PWM so I think the 50Hz sinewave can also be used to modulate its high frequency output. Then a simple high frequency output filter can smooth it into a pure sinewave.
Why don't you find then copy the circuit of a pure sinewave inverter that might be using an SG3525?

 

[princeguru]

Re: Generating spwm using 555 timer and 8038

The SG3525 regulates its output voltage with PWM so I think the 50Hz sinewave can also be used to modulate its high frequency output. Then a simple high frequency output filter can smooth it into a pure sinewave.
Why don't you find then copy the circuit of a pure sinewave inverter that might be using an SG3525?

Ok can i use 8038 to generate my 50hz sinewave and pass it through the op-amp then after that i filter it using high frequency filter as for the copy of circuit sinwave using sg3525 i dont know how to get it can you please help me get it if you have any please

 

[Audioguru]

Re: Generating spwm using 555 timer and 8038

Why do you have an opamp? You need a comparator instead.
Have you heard about Google? I looked in Google for "SG3525 pure sine wave inverter circuit" and found hundreds of them. Some of them work properly.

- - - Updated - - -

Why do you have an opamp? You need a comparator instead.
Have you heard about Google? I looked in Google for "SG3525 pure sine wave inverter circuit" and found hundreds of them. Some of them work properly.

EDIT:
What is the matter with this website? It takes a long time to respond then says, "Do you want to stay or leave?".