What would you want to see in a specification for a dc-dc converter? 2

[bpelec]

If you were a customer, buying a custom made dc-dc converter for an application, what information would you want to see in an outline specification? By "outline specification", I mean the kind of thing that would come along with a quote, before a final system design had been agreed.

I am writing such a specification, but it is my first and I am not sure what level of detail to go into. For example, it seems obvious that I would include the input and ouput voltage and current requirements, but should I include percentage voltage ripple and EMI (I have no idea what the EMI will be like yet)?

Thanks for your help.

Best regards,

BPELEC.

 

[Skogsgurra]

Is this a DC/DC "isolation amplifier" for measurement purposes? Or is it a power device? For instance 24 V in 5 V out at some specified current?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[bpelec]

Input: 26-30 Vdc
Output: 28 Vdc @ 5amps

The converter must use a transformer, and the primary and secondary sides are therefore isolated.

 

[ScottyUK]

Add the following:

Input voltage range, minimum to maximum.
Output regulation under load change
Output regulation under input change
Behaviour under short circuit: shut down, burn out, blow up, etc.

Why not pick a manufacturer datasheet for a similar product from one of the numerous manufacturers: Astec Standard, Power One, Artesyn, Vicor, etc and see what they include. That will give you some idea what you need to achieve and what you need to show on the datasheet.

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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

What you do is.. Find a similar unit that is off-the-shelf. Then you duplicate the spec. You then whack out all/any of the items you don't care about. You modify the others. This is really the only way to go because there's no way you will be able to sit there and think of all the different details generally needed.

I would go further to find the data sheet of a device made by a likely company you might want to use. If you generate the spec from their original specs, it will greatly reduce your expense because they will have a solid clear feel for what you want and will immediately be thinking of how to tweak an existing device to meet your needs. This will probably knock 50% or more off the "otherwise" price.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[bpelec]

Yes, a good idea ScottyUK, and thank you for the suggestions.

Best regards,

BPELEC.

 

[Skogsgurra]

I like to see:

Input voltage range.
Output voltage tolerance and regulation.
Minimum load. Maximum load.
Ripple at minimum and maximum load.
Current limit, overload capability.
Efficiency at selected load points and input voltages.
Output impedance (over a frequency range).
Transient load response. Both applying load and releasing load. Overshoot in the latter case may be very important.
Isolation voltage between primary and secondary.
Capacitance between P and S. Also leakage current (if for medical purposes).
Input current waveform is probably not a problem - but nice to have in spec.
Temperature range storage and working.
Thermal resistance.
Vibration.
Humidity.
Dimensions.
Weight.
Price.

I have probably forgotten a few things. I hope that others will fill those in. Do study the data sheets from competition. That will give you some hints.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Dang! Cross posticated..

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[bpelec]

Great stuff! Thank you all.

 

[Skogsgurra]

Are we exhausted?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

No! (not now)

You left out "Approvals". Another reason you may want to use a tweaked off-the-shelf model as you/they could probably just ride thru on some/all of the approvals.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Skogsgurra]

Yes, of course. Approvals! They seem to be more important than technical specs nowadays.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...