Simple pwm control 2013-01-17

[alec_t]

alec_t submitted a new article:

Simple PWM control - Here's a simple PWM control circuit using inexpensive readily-available components.

The circuit component values shown are for a 12V supply but could be altered for other supply voltages less than 15V.
Most of the work is done by a CD40106 hex Schmitt inverter IC.
U1a/R1/C3 form an oscillator running at ~22kHz. Its square-wave output is integrated by R2/C4 to give an approximation of a triangular wave. This wave is summed at the input of gate U1b with a...[/quote]

Read more about this article...

 

[etofix dee]

please can any one send me a comprehensive circuit diagram for a 3-phase DC-AC inverter. most probably 15KW

 

[alec_t]

alec_t updated {articleTitle} with a new update entry:

... an even simpler PWM pulse generator

A second voltage-controlled PWM generator circuit added to the original simple PWM generator article. It uses only one CMOS Schmitt gate, three resistors and one capacitor!

Read the rest of this update entry...

 

[alec_t]

You are more likely to get help if you start your thread inside the appropriate forum; not in an Article.

 

[Kevin O'Brien]

Nice circuit. I could not understand this for a while. But I think I get it now, very neat. I am assuming that the power to drive the oscillator is provided by the power within the Schmitt comparator? So at t=0 the output of it is high which starts the oscillations going. Is that right?

 

[panic mode]

Lol...

 

[Gasboss775]

I tried to make a PWM circuit using the same basic structure as you, but I must have been off with my component values as I couldn't get the same range of duty cycle that you've achieved. I will try out your circuit soon.

 

[4pyros]

3 Phase Help??

 

[Gasboss775]

I've had similar results as you with the second circuit, about 10~90% some variation of the operating frequency too.

 

[Menticol]

please can any one send me a comprehensive circuit diagram for a 3-phase DC-AC inverter. most probably 15KW

Here's a comprehensive picture of what you are looking for

View attachment 64226

 

[Gasboss775]

Today I tried your first circuit, using your exact component values ( all 1% including the two 1n capacitors ) These were my results:

I can only assume that our differences are due to different thresholds in our 40106's. I think the tolerance of the set points is quite wide. I might mess around with component values again to see if I can do any better.

 

[Gasboss775]

Changing the 430K resistor to 360K yielded better results for me.

 

[Gasboss775]

Just had a look at the CD40106 datasheet, The spread of the trigger points is very wide. For VDD=15 V;


Upper threshold can be from 6.8 to 10.8 V That's +/- 23%!! Lower threshold can be from 4.0 to 7.4, That's +/-30%

So anyone building this may need to play around with the component values. The circuit makes a good led dimmer ( you wouldnt need the output transistors except for the case of power LED's. )

 

[johnyradio]

hi, what program produced these .asc files? I'm having trouble importing them.

thx!