Author Topic: Stable Gated PWM Progress  (Read 18610 times)

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Stable Gated PWM Progress
« on: February 21, 2009, 17:38:25 pm »
I'm working on a new stable Gated PWM.

We all know that Lawton's gated PWM has major flaws, including;

when one adjusts the frequency, the pulse width ratio also changes, for example you can have a 50% duty cycle, and as one changes the frequency, the duty cycle also changes.

my goal with this new circuit is to keep the duty cycle ratio the same as the frequency is adjusted for both, the main frequency and for the gating frequency. Also the pulse width can be changed and the freq stays the same.

I have done some progress and have the circuit almost done, just need to fine tune some components.

here are some shots:

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Re: Stable Gated PWM Progress
« Reply #1 on: February 21, 2009, 17:42:26 pm »
As soon as I have it fine-tuned I will post the schematic.

It will use two 555 and two LM311 chips.

I'm trying to get the circuit to operate in a very large range of freq.



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Re: Stable Gated PWM Progress
« Reply #2 on: February 21, 2009, 18:08:30 pm »
Donaldwfc, to make you feel better, I'm no electronics expert, I'm also learning as I experiment. what helps me the most is that I'm a programmer so I apply my programing logic to electronics, it is very similar. each electronic component performs a function similar to functions in programs.

This circuit will be very easy for anyone to build.


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Re: Stable Gated PWM Progress
« Reply #3 on: February 21, 2009, 18:21:33 pm »
I'm glad It helps.. and on the same idea, some IC chips can have several functions and others only one function.

For example the LM311 that I'm using, its function is to compare 2 volatges, once one voltage hits a threshold, it turns on an internal switch. below the threshold, the switch is off.

There are many ways of doing the same thing, just like in programing.
we just have to get creative.

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Re: Stable Gated PWM Progress
« Reply #4 on: February 21, 2009, 18:34:07 pm »
As soon as I have it fine-tuned I will post the schematic.

It will use two 555 and two LM311 chips.

I'm trying to get the circuit to operate in a very large range of freq.


Electrojolt , we dont need super high freq , something like 1khz to 150 khz sounds good .

Thx so much for this , we will pay you back.

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Re: Stable Gated PWM Progress
« Reply #5 on: February 21, 2009, 20:33:46 pm »
dankie is correct.. technically we only need around 0-20 khz by what stan says but it would be nice you go a little further past that just to have it..  thank you for applying your expertise in fixing this problem.. 


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Re: Stable Gated PWM Progress
« Reply #6 on: February 21, 2009, 20:38:28 pm »
I'm working on a new stable Gated PWM.

We all know that Lawton's gated PWM has major flaws, including;

when one adjusts the frequency, the pulse width ratio also changes, for example you can have a 50% duty cycle, and as one changes the frequency, the duty cycle also changes.

my goal with this new circuit is to keep the duty cycle ratio the same as the frequency is adjusted for both, the main frequency and for the gating frequency. Also the pulse width can be changed and the freq stays the same.

I have done some progress and have the circuit almost done, just need to fine tune some components.

here are some shots:

Great idea. The non synchrone adjusting of the DL circuit was always a problem!

br
Steve

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Re: Stable Gated PWM Progress
« Reply #7 on: February 21, 2009, 20:52:17 pm »
Well, the 555 chip I'm using can go up to 2.4 Mhz.  so we have plenty of room. now I just have to find out how far I can push the LM311.