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Registered Member #3334
Joined: Tue Oct 19 2010, 02:24AM
Location: Colombia
Posts: 17
Hi Grenadier,
I have used something similar; I set two flybacks, the primaries in parallel and the secondary in series, obviously with their respective ZVS drivers using four MOSFET transistors, but It looks like It has not reach the necessary voltage to shoot electrons from the catode to the anode.
Have you tested your design?, I can provide you the components I used and we can share experiences. Please check our design.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
The easiest way to achieve the necessary voltages is with an AC high voltage source and a multiplier. Series-connected flybacks is risky; the secondaries might be damaged by overvoltage. Perhaps a 12KV NST and a 4-stage multiplier? That should give you 69KV peak and ~7 mA current.
a portable dental X-ray machine must have "type approval" and conform to national safety standards for use on human beings, so you will have to design your product around the 'type approval' criteria and national standards of Colombia.
In practice, 'type approval' criteria are much the same from one country to another, and you should examine machines currently authorised for use in Colombia to see how the designers have approached the problem of meeting type approval standards and safety standards.
Type Approval and safety certification examinations by government agencies are always very expensive, and can involve submitting a number of machines for examination.
Here is a Type Approval application form from India, which must stand in for many like it from other nations:
China is the present market leader in lightweight portable dental X-ray equipment, and is able to offer machines at such low prices it would be hard to find a way to compete with them:
Notice that the mounting type specified for Canadian sales is different "Ball- 2009140* Spiral (excluding Canada longituba)" - clearly to meet a Canadian Type Approval criterion.
Trust me, you will, thankfully, never get Type Approval for a portable dental X-ray machine made out of scrap,
Registered Member #3334
Joined: Tue Oct 19 2010, 02:24AM
Location: Colombia
Posts: 17
Hi,
Well, I realized that using flybacks is not a good option few months ago; however, it is a good way to start designing and understanding the principles of high frecuency techniques, I have been through legal procedures because we have a 510k FDA approval. Once, I bought UHV-11A capacitors (1000pF@50kVp) and some fast diodes but this solution is not very effective, I did import the lightweight portable dental X-ray equipment you mentioned; but it is not really portable beacuse it is composed by a mainframe and a head: the weight is nearly 11 kg. I know that Medium-frequency generators, CW multipliers and Constant potential generators are commonly used in these applications; but I do not know how to start.
I contacted some chinese FBT manufacturers but it seems they do not know much about customized designs;nonetheless, there is an american company that manufactures power supplies like: HVP080 and XRS050N200, have a look at them, the problem is that these devices cost over 1800 USD each. Do you think buying one of these will help?.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
You should look at the construction - and any patents - for The Aribex Nomad Pro Handheld intraoral dental X-ray Unit which has a 60kV/2.5mA source, weighs 2.5kg, looks much like a handheld XRF analyser, and costs US$6,495:
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