Looking for Analog to PWM signal -

  • Thread starter Windadct
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  • #1
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Hello All:

This may be a repeat post - I looked at my history and did not see it.

I am looking for a product ( finished/qualified) that takes a standard Analog signal ( 0-10V and/or 4-20mA) and converts to a PWM signal with fixed but settable; Frequency of ~ 100 to 5000hZ - possibly with a dip switch.

For example - if using the 0-10V input - at 5V the PWM signal has DS of 50%.

Needs to be hardwired - not a programmable device. In some circles this would be considered a signal conditioner.
 

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  • #2
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Hi,
You can do this with a 555 timer and a comparator.

You configure the 555 timer to generate a sawtooth waveform, and you feed that waveform into the - input of the comparator, and then your DC voltage setting on the +. As you decrease the voltage level, the ramp voltage will hit it faster each cycle and turn the comparator off for a longer % of the cycle.

I don't know of anything fully qualified since this is a pretty simple circuit that anyone would just make probably.
 
  • #3
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Hello DP - Thanks - Yes I am sure to make one would be pretty basic, this is for a Power Electronics application where the components must be "Qualified Products" For us to do even a basic PCB and qualify it ~ 5 to $10K. Controlling a 100KW DC Power Supply application - where a Miss-operation would be a disaster.
 
  • #4
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Here is a circuit to do what I described.

You can ignore the output end with the 10k load, I used all of that for level shifting and protection only. If you use a single ended supply you would have less to worry about with that. The sine wave represents the adjustable DC voltage reference operating range. R1 and C1 set your frequency. The diode D1 shorts the high end of the resistor divider inside the 555 timer close to 0 to get fullest range.
 

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  • #5
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Hello DP - Thanks - Yes I am sure to make one would be pretty basic, this is for a Power Electronics application where the components must be "Qualified Products" For us to do even a basic PCB and qualify it ~ 5 to $10K. Controlling a 100KW DC Power Supply application - where a Miss-operation would be a disaster.
Oh I see, then you'd definitely want to buy something already made or refine your own design a lot.

I'd say just use a modern signal generator, but that is not cheap itself. If miss-operation would result in disaster, I think this forum is not the right place to find your answers since someone fully qualified already should be making this decision. Something that is fully qualified never comes cheap.
 
  • #6
dlgoff
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Axiomatic makes the "www.axiomatic.com/current-pwm-converter.pdf" [Broken] and the "www.axiomatic.com/TD2002AX.pdf" [Broken] signal conditioners.
 
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  • #7
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Hello again - I think Dlgoff has provided a good product to consider - Thanks! I am pretty good at web searing but this has eleuded me - it is actually reference to my customer, we just make the power stages. I thought someone may have seen such an animal. As for the actual circuit and design - yes I did need a robust solution, so I was more looking for a reference to an existing product than circuit / design advice.

Thanks Again!
 

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