High voltage, low current reference.

Go To Last Post
9 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Freaks,

I need to create a high voltage (350VDC), low current ( 1ma - 7ma ), current source. Accuracy is not critical but stability at varying voltages is important.

I realize beggars can't be choosers but I have some HV enhancement mode MOSFETs in the circuit. I would like to use one of these if possible.

Any suggestions?

Thank you,

A.

AVR Studio 4 Ver. 4.18 684
avr-gcc Ver. 4.3.0
ISIS 7
ELECTRA

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I'm assuming you don't just want to buy one? (ie HP 6186C) Are you worried about generating the 350V, or just about regulating the current?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You need a boost converter. This is a common form of switching power supply. You need a mosfet, inductor, diode and a source of pwm. Something like a mc34060 ic would do it.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Is the load grounded or floating?

Does the current source have to be high-side or can it be low-side?

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Jim,

The source is high side with load connected to ground. The 350VDC is not a problem. I have a stable supply for this.

What I am looking for is something similar to the attached circuit. It works somewhat better than a simple resistor but still has error equivilant to the gate resistor current.

Any suggestion on how to improve on what I have so far?

Thanks all.

A.

Attachment(s): 

AVR Studio 4 Ver. 4.18 684
avr-gcc Ver. 4.3.0
ISIS 7
ELECTRA

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

That should work pretty well. It will shift some if your load goes from a 300V drop to a 30V drop, but way better than a resistor. I was going to suggest something along those lines.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Jim,

Thanks,

A.

AVR Studio 4 Ver. 4.18 684
avr-gcc Ver. 4.3.0
ISIS 7
ELECTRA

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Some voltage regulators can be configured to be current regulators.
Supertex LR8 (data sheet, go to page 4, Figure 3: High Voltage Adjustable Constant Current Source)
A switcher would be more efficient if interested.
High voltage DC-to-DC or off-line (wall power) AC-to-DC from Power Integrations, On Semiconductor, etc.
Some of these are designed for LED (constant current) drive.

http://www.diodes.com/catalog/linear_led_drivers_182/
Maybe could create a discrete version of the AL5802 (or AL5801?).
A current sink though can be used as a current source.

"Dare to be naïve." - Buckminster Fuller

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

gchapman,

I didn't know 3 terminal regulators were available to this high a voltage. I will order a couple and tinker with them. It is probably a better solution than the descrete circuit.

Thank you,

A.

AVR Studio 4 Ver. 4.18 684
avr-gcc Ver. 4.3.0
ISIS 7
ELECTRA