# how to step up 5VDC to 100-200VDC? (for APD)

Discussion in 'Electronic Design' started by Michael, Jun 2, 2007.

1. ### MichaelGuest

Hi there - I need to make an adjustable DC power supply that takes an
input of 5V and have an output of about 100-200V. I'm not sure on the
exact voltage yet - ideally it'd be adjustable. I would like ripple to
be as low as possible, ideally in the mv range. Admittedly I don't
know exactly how low ripple needs to be, so I would like to err on the
side of low ripple. Current will be very low, under a ma I believe. I
think microamp or nanoamp range. This will be the power supply for an
Avalanche Photo Diode (APD). I haven't chosen a specific one just yet.

Is there a standard/accepted way of doing something like this? I've
seen some people create an AC signal, run it through a transformer
that steps up the voltage, and then rectify/smooth that. Is that a
good way, or are there better ways? Are there any parts I should be
looking at, or application notes, or anything like that? Thanks!

-Michael

2. ### D from BCGuest

I'm guessing the classic "boost" switch mode power supply to convert
5V to 100 to 200V.
D from BC

3. ### Martin RiddleGuest

Piezo? http://www.zippy.com/Cer_INDEX.asp?lv_rfnbr=2

Ok its neat but too much for your application.

Stepup transformer is the way to go. If you had more than 5 volts you could
use a voltage multiplier.

Cheers

4. ### colinGuest

http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF

app doesnt show high voltage supply but use
with either a small step up transformer or a voltage multiplier, or both.

Colin =^.^=

5. ### Jan PanteltjeGuest

Eh, I take small potcore (rip from old PCB or something).
5 turns primary
100 (or 200) turns secundairy
1 turn feedback

The circuit:

1t 5t 200t
+5V-- ----------------
|+ | 4k7 | L1
10u === [ ] R1 | ) | --------------- a diode k ---------- + 200V
--- |_____ | ) | ( |
tant | C1 | ) | ) | ( === 400V poly
/// | -- | ) | (_______________________________| C4
| | |------------- |
| | c | ///
| ---b NPN Si |
- | e T1 ===
--- 10u | |22n
=== 5V | | Poly
+ | C2 | | C3
/// /// ///

C1 decouples
C2 is 'upside down,. the top will become negative.
C3 set frequency (sinewave), several kHz, do not use ceramic, too many losses.
C4 should be able to handle your volts, and Q= CxU = i x t helps you estimate the ripple.
R1
T1 can be any low power si NPN that can handle some 45 V
Waveform is close to sinewave (bottom slightly flat).
L1 is simply 1 turn per volt.
If it does not oscillate reverse the feedback loop connections before the transistor evaporates.

I have used this many times.... even in EPROM programmer.
If you know how to wind some turns of wire you can build it in a few minutes,

6. ### MooseFETGuest

Beyond about a 10:1 ratio, the classic boost regulator isn't going to
be very good. There are several things that start to work against
you.

Basically what is happening as the ratio goes up is that the high
frequency content of the switching waveform is increasing. This puts
extra requirements on all the parts that see the wave form.

The output rectifier has to handle narrow pulses of quite high
currents. The power in the diode follows a function between the
average and RMS current since the forward voltage on it is not a
linear function of current, but you still end up needing a bigger
diode. Bigger diode tend to be worse from a high frequency point of
view.

The high voltage requirement on the inductor may cause trouble.

If the OP only needs small currents, a voltage multiplier on the
output may be the way to go. At higher currents, a transformer is
needed.

7. ### Guest

Have a look at app note 98 from Linear Technology - there is a 0-300V
low noise circuit - good stuff!

MJ

8. ### Barry LennoxGuest

It could be worth looking at the disposable flash camera boards.
Asking nicely at a photo processor normally gets you several. They use
a single AA cell and generate about 300 volts, If your current is
only uA or nA just use a divider to get what you need.

You can get some ideas from

http://www.increa.com/reverse/dc/
http://www.geocities.com/lemagicien_2000/elecpage/maxflash/maxflash.html
http://members.misty.com/don//kmaxhack.html

Barry