High Voltage Unipolar Sine Wave

[nutellaaxis]

Hello!

I'm trying to generate a low power, high voltage sine wave that is unipolar (so, peak to peak ranges from 0V to 300V). Ideally, I would like the ability to vary the frequency from 10Hz to 60Hz.

Is there an ideal method of doing this?

With lower voltage I would generate my sine wave (bipolar), then use an op-amp to amplify it as desired, and also add a DC offset to make it unipolar... but I don't know of any op-amps that can handle the voltages I am interested in.

I can easily make my sine wave at low voltage, then amplify it to -150V to 150V using a transformer... but can this be offset to 0V to 300V?

or

I can generate a low power 300V DC signal... but can I make a 0V to 300V sine wave out of this?

Thanks for any advice!

 

[berkeman]

Hello!

I'm trying to generate a low power, high voltage sine wave that is unipolar (so, peak to peak ranges from 0V to 300V). Ideally, I would like the ability to vary the frequency from 10Hz to 60Hz.

Is there an ideal method of doing this?

With lower voltage I would generate my sine wave (bipolar), then use an op-amp to amplify it as desired, and also add a DC offset to make it unipolar... but I don't know of any op-amps that can handle the voltages I am interested in.

I can easily make my sine wave at low voltage, then amplify it to -150V to 150V using a transformer... but can this be offset to 0V to 300V?

or

I can generate a low power 300V DC signal... but can I make a 0V to 300V sine wave out of this?

Thanks for any advice!

Use the transformer to make the high voltage sine wave, and connect a HV DC power supply to one side of the transformer. Set the DC power supply to 1/2 of the Vpp out of the transformer...

 

[vk6kro]

One way would be to find a device that will work as an amplifier with a 300 volt supply.
The preferred device would probably be an insulated gate FET.

You could then use a resistive load and just take the ourput from the drain of the FET.

I have problems with using a transformer at 10 Hz, especially if it has DC current flowing in it, but you might get away with it.

 

[rude man]

Just to amplify on berkeman: connect the primary wires to your ac supply. Connect one of the secondary wires to a 150V wer supply, and use the other secondary wire as your output. Adjust the ac input to give you the drired 300V pk-pk voltage.

 

[berkeman]

I have problems with using a transformer at 10 Hz, especially if it has DC current flowing in it, but you might get away with it.

Yikes. I missed the 10Hz part and tunnel-visioned on the 60Hz part. Good catch vk6kro.

 

[yungman]

It is all about money. Apex make +/-200V op-amp for long time. You use +310V and -15V supply to power up the amp and just design like a normal op-amp with offset.

I designed discrete op-amp with bi-polar transistors to drive 0 to 300V.Transformer might not work well for 10Hz. You need to design a closed loop feedback to control the amplitude and a very strong drive to drive the transformer. At the end of the day, it is going to be more complicated than designing a discrete op-amp using high voltage transistors.

 

[vk6kro]

It is probably a good application for a vacuum tube. These are still available and there are plenty of them that would cope with 300 to 400 volts. Look for small transmitting tubes like the 6146.

Just drive the vacuum tube from fully on to fully off with a resistive load and take the output directly from the plate.

It is all about money. Apex make +/-200V op-amp for long time. You use +310V and -15V supply to power up the amp and just design like a normal op-amp with offset.

I designed discrete op-amp with bi-polar transistors to drive 0 to 300V.

Thanks Yungman. I didn't know they had opamps with such high voltage capability

 

[yungman]

Here is the link. I used a lot of their op-amp, but they were expensive and we used it with other high voltage stuff and we burnt a lot of them due to arcing. I finally changed to a discrete design that can take a beating.

http://www.cirrus.com/en/products/power_operational_amplifiers.html#PA160_stDiv

 

[Bob S]

This isn't exactly a sine wave, but it does convert a 15V sine wave to a voltage that ranges between 0 volts and 300 volts at 50 kHz.

 

[Bob S]

As suggested before.