Re: Power supply design problem
- From: Wimpie <wimtel@xxxxxxxxx>
- Date: Tue, 26 Feb 2008 12:46:42 -0800 (PST)
On 26 feb, 17:03, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
On Tue, 26 Feb 2008 07:25:18 -0800, Gundal21 wrote:
Hi,
This is my first question in this groups. Because my mother tongue is
not english, I'm afraid whether my question will be well expressed or
not.
Your writing has a bit of an accent, but it is quite clear.
The question is as follows. My major interest is mechanics. But since I
have so much interest in electronics, I've been studying electronics by
myself.(It's really exciting for me, fortunately.) Recently, I've been
making a power amplifier for ultrasound applications.
Using power op-amp the main amp parts are almost finished. But I want to
make my power amp as compact as possible. The problem is a power supply
system. I'm using the commercial power supply system which can be used
for very wide range of applications. I want to make this power system of
my own. Is it sufficient to use a power supply circuit which is consist
of transformer, bridge diode, and
some filtering components as capacitor and inductor? Since the required
output voltage is about 80V or more, semiconductor based
chip such as 7805 or LM317 is impossible. The power amp will generate
pulse signals of some hundred kHz and the required
current will be 1~3A.
Can you recommend any source circuit or textbook or internet site?
Please help me.
Depending on the amount of regulation you need you can just use a filter
capacitor, or a filter capacitor and an inductor. You can also build a
high-level linear regulation circuit based on an LM723 if you're careful
about how you go about it. If you _really_ want to go overboard you
could build an off-line switching regulator, but that would be much more
involved than the rest of the project, combined.
If you can get surplus parts where you are, consider using a pair of 48V
switching supplies. They're often isolated so you can connect their
outputs in series for 96V (I'd verify isolation first, though).
Be careful -- you're definitely getting into voltages that'll hurt if you
come into contact with them, and could be fatal on a bad day. You may
want to google around for safety rules & see if you can find them.
--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com
Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html
Regarding safety, go for ECMA 287 from ecma international. It is
almost similar to IEC 950, but free. Regarding a non regulated
rectified supply. Note that the no load rectified voltage can be about
30% above the full load voltage. Also, you cannot fully load the
transformer. When you have, for example, a transformer that can
deliver 10A ac, you can load it with about 6.6A DC when using a full
wave rectifier with storage capacitors. also take into account mains
supply variations. when you require at least about 80V (regulated)
output voltage, your no load rectified voltage will be in the 120V
range. This aren't SELV levels.
When you want to make a compact regulated power supply that is able to
deliver the required load for a long time, you may consider a switched
regulator (as Tim suggested). This type of regulators require
reasonable experience.
If it is a commercial project, you may consider contracting somebody
that is into MOSFET class D, E amplifiers (as sine wave output is
required). They have a high efficiency (over 85%) and therefore do
not need much cooling provisions.
Best regards,
Wim
PA3DJS
www.tetech.nl (Dutch)
.
- References:
- Power supply design problem
- From: Gundal21
- Re: Power supply design problem
- From: Tim Wescott
- Power supply design problem
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