Flyback Convertor Help

Dear Friends,
I need a help. I am trying to design a charging circuit for a defibrillator using a flyback topology. I need to use a battery (12V or 24V) to charge a 150uF capacitor to 300J under 2000V with a switching frequency of 100KHz (or higher) within 6-15 seconds. I am not so familiar with flyback topology, and I need any suggestion related to how to design the circuit, required parts, how to stimulate it in orcad, or any kind of help.
Thanks in advance.

That's <20W! It should be a piece of piss!

It should be easy to make, there are some ICs from Linear, Maxim etc. that can do this. However, this is as piece of medical equipment so you should buy from a suitable supplier as it will suitably be approved, if someone is killed because you've used a home-build appliance on them then you could be locked up for a long time.

Do you have the propper training to use auch a device? If not then you should leave it well alone.

Is the purpose of a defibrillator to stop the heart momentarially? The hope being that after the heart-stopping shock, the heart starts beating again, in a more normal rhythm. So every shock is a split-second of death...

HarveyH42 said:

Is the purpose of a defibrillator to stop the heart momentarially? The hope being that after the heart-stopping shock, the heart starts beating again, in a more normal rhythm. So every shock is a split-second of death...

Click to expand...

They are unfortunately almost always shown incorrectly on TV and films, the patient flat lines and the defibrillator is used to restart it.

This isn't how they work!.

The name gives it away really, 'defibrillator' - it's used to treat a heart that's in 'fibrillation' - beating uncontrollably, more a fast 'flutter' than a beat.

The heartbeat should be controlled by the brain, rather like a timer interrupt routine in the brain However, if the heart doesn't receive signals to beat, it can generate it's own 'signals', this is what fibrillation is - the heart controlling itself badly, rather than the brain in charge. So the defibrillator is used to stop the heart, and allow the brain to take control again.

(Crude explanation, but that's the basic idea).

Modern portable units are extremely easy to use, you open the lid and it's got instructions printed there, and if you can't read?, it will even give you verbal instructions. Basically you place the electrodes where it tells you, then press the button - the unit checks that the heart is in fibrillation, and only then gives the shock - so it's really pretty fool proof (but expensive).

Obviously they are stuffed full of electronics, I wonder if they use PIC's?.

Nigel Goodwin said:

They are unfortunately almost always shown incorrectly on TV and films, the patient flat lines and the defibrillator is used to restart it.

This isn't how they work!.

The name gives it away really, 'defibrillator' - it's used to treat a heart that's in 'fibrillation' - beating uncontrollably, more a fast 'flutter' than a beat.

The heartbeat should be controlled by the brain, rather like a timer interrupt routine in the brain However, if the heart doesn't receive signals to beat, it can generate it's own 'signals', this is what fibrillation is - the heart controlling itself badly, rather than the brain in charge. So the defibrillator is used to stop the heart, and allow the brain to take control again.

(Crude explanation, but that's the basic idea).

Modern portable units are extremely easy to use, you open the lid and it's got instructions printed there, and if you can't read?, it will even give you verbal instructions. Basically you place the electrodes where it tells you, then press the button - the unit checks that the heart is in fibrillation, and only then gives the shock - so it's really pretty fool proof (but expensive).

Obviously they are stuffed full of electronics, I wonder if they use PIC's?.

Click to expand...

not quite, the heart is a self-regulated organ no stimulus from the brain is needed. The only way the brain has any influence over the heart is through adrenalin release.

I have been a First-aider at work now for 6years and 4years ago we were given those portable defibs (and first-aiders given training every 6months). They really are fantastic pieces of kit!. They can deliver enough charge in one blast to (momentarily) light wembly stadium (well maybe the old one) and have enough charge is their Li-ion battery for something like 100 charges. It really is plug and play talks you through it and all that

each heart-cell actually generates a pace-maker pulse which "Should" be in sync with all around. IF some tissue gets starved (say due to an MI) then part gets isolated and starts beating at it's own rate (un-regulated by the masses), this then has the possiblity of throwing the rest into chaos (likewise the rest can re-sync the damaged part) and the whole heart goes into spasm... an MI

only two rythems are shockable (NOTE rythems, you won't get someone back via fibulation if they are flatline... but you might via heart massage) and this little box knows them and won't let you shock if it doesn't detect one, and advises if it thinks you have to