Voltage Divider

[ajaba]

Hello,

I have two piezoceramic materials with different voltage rating; One of them requires a voltage range from 0-1000V (1kV rated) and the other one has 0-500V (500V rated).

I have an amplifier that can go from -500 to 1500 V.

Question: Does my suggested circuit do the job?

I have attached two different scenarios; without diode (case#1) and with diode(case#2).

Why diode: to protect the amplifier from piezo discharge. But when I put diode the voltage
difference across (500V rating piezo) will go from 1kV to 1.5kV (still 500V voltage difference) but
I do not know if this damages the piezo meaning that instead of using 0-500V using 1kV-1.5kV
(same voltage difference)?

Thanks for your time looking into my case study.

[MarkT]

I see no diode. Why is the supply going negative if your devices are only rated for positive voltages?

[ajaba]

MarkT:
I see no diode. Why is the supply going negative if your devices are only rated for positive voltages?

Thanks for reviewing my post and sorry for the mistakes. It should be OK now.

thanks,

[raschemmel]

I have two piezoceramic materials with different voltage rating;

and the other one has 0-500V (500V rated).

One of them requires a voltage range from 0-1000V (1kV rated)

I have an amplifier that can go from -500 to 1500 V.

Question: Does my suggested circuit do the job?

What 'job' would that be ?

What is the function of the circuit ?

[Paul_B]

raschemmel:
What 'job' would that be ?

What is the function of the circuit ?

Excellent questions I say!

[ajaba]

Paul__B:

Excellent questions I say!

"do the job" means provide required voltage for both piezos. One option is use one amplifier for each piezo(2 piezos so 2 amplifier) but I wanted to run simultaneously two piezos with different rating voltage with one amplifier. Hope it is clear.

[MarkT]

Now you are running the amplifier between 0V and 1.5kV isn't case 1 correct? Previously you had it
oscillating between -500V and 1.5kV.

[ajaba]

MarkT:
Now you are running the amplifier between 0V and 1.5kV isn't case 1 correct? Previously you had it
oscillating between -500V and 1.5kV.

Yes, theoretically seems fine

But is it good enough or do I need to worry about anything else.

Another question is that do I need a diode?

I am also curious to know why diode changed the voltage behavior.?

[MarkT]

The diode charged up the capacitor with a DC offset.

For stable voltages you'll probably need bleeder resistors across the capacitive divider, around 10M or so high
voltage types, to swamp the leakage currents and define a DC division ratio to match the ac ratio.

[raschemmel]

What is the signal FREQUENCY ?

[raschemmel]

Since you didn't give a frequency I used 3000 Hz
It works at that frequency.

The simulation was tested by changing the cap values and observing the output voltages for Vout_500v and
Vout_1kV.

[ajaba]

raschemmel:
Since you didn't give a frequency I used 3000 Hz
It works at that frequency.

The simulation was tested by changing the cap values and observing the output voltages for Vout_500v and
Vout_1kV.

Thanks for the simulation. Your simulation result agrees with mine which means that the circuit should work (right?). My range of frequency was lower than 200Hz since you asked.

[ajaba]

MarkT:
The diode charged up the capacitor with a DC offset.

For stable voltages you'll probably need bleeder resistors across the capacitive divider, around 10M or so high
voltage types, to swamp the leakage currents and define a DC division ratio to match the ac ratio.

Thanks for your reply. I am not sure if I understood it correctly. Is it possible to do it in a sketch?

[raschemmel]

Here's 200Hz

[raschemmel]

This is what happens when you add the diodes:

The diode charged up the capacitor with a DC offset.

The DC offset is clearly shown.

[ajaba]

raschemmel:
This is what happens when you add the diodes:

[raschemmel]

It would appear it is half wave rectification, but don't quote me.

[ajaba]

raschemmel:
Since you didn't give a frequency I used 3000 Hz
It works at that frequency.

The simulation was tested by changing the cap values and observing the output voltages for Vout_500v and
Vout_1kV.

What is the small arrow in your sketch:

Thanks,

raschemmel:
Here's 200Hz

What does the arrow at C2 and C4 stand for? I am trying to re-do your sketch in LTspice and wanted to know the role of those arrows.

Thanks

[raschemmel]

What is the small arrow in your sketch:

What does the arrow at C2 and C4 stand for?

The are just ground nodes. They represent where the oscilloscope ground or meter ground lead would go
if you were measuring the voltage on a real circuit. (probably unnecessary for this case)

Ignore the arrows and ask yourself how you are going to put the piezos in your LTSPICE circuit ?
(good luck finding them in the component libraries)