High-Voltage Sawtooth
Waveform Generator
This
project is being done for the Montana State University Space Science
and Engineering Laboratory (SSEL), they have requested the construction
of a high-voltage sawtooth waveform generator to bias a Lnagmuir Probe
on a research satellite.
The product is to be designed around the following criteria.
- Operate over a frequency of 100-2500Hz
- Have a varying output with a maximum and minimum of +40v and
-40v
- Operate off of three analog 0-5v control lines that will
control the frequency, minimum and maximum output voltages.
- Have small enough component selection to be able to fit
within a 4"x4"x4" cube
- Be able to operate predictably over the great temperature
ranges of space.
- Operate off of the satellite DC voltages of ±3.3v,
±5v, ±12v
- Power consumption must be under 1.5W due to the battery
operated nature of the satellite.
Major system components.
- DC-DC power supplies
- These power supplies must take the voltage supplied by the
satellite and convert it to the ±40vDC needed for the amplifier
circuit.
- The power supplies are constructed using a combination of
a 555 timer, a 741 opamp and a cascading voltage multiplier.
- The 555 timer creates an oscillation that is fed into the
741 to create a waveform that runs between ±12vDC.
The AC waveform is fed into two cascading voltage multipliers to create
the positive and negative 40vDC sources.
- High-Voltage Amplifier
- Due to the low frequency nature of the design a simple
push-pull amplifier will accomplish the task here.
- Waveform Generator
- We are using an Analog Devices AD537 voltage to frequency
converter that outputs a square wave for our timing for our switch.
This is placed across our timing capacitor which creates a floating
node that has a linear ramp. By using this we can have a perfectly
linear output with no distortion that is highly scalable. We then feed
this into our Analog Devices 534 to multiply an offset before finally
feeding this waveform into the push-pull amplifier.