Efficiently charge electrolytic capacitors

Hi

Im looking for a suitable IC to charge electrolytic capacitors to a voltage of 30-40V in constant current mode. As an input I intend to use a 12V voltage regulated power supply.

Regarding voltage regulators, there are not many around which go up to 40V. So far, I have found the LM2733, but the output current is only around 300 mA. Maybe I have to use an IC with external switch?

To summarize:
Vin = approx. 12V (regulated)
Vout max = 38V
IC cost: < $3
Constant Current Mode
I > 0.5 A

Any suggestions for specific ICs or how I can find suitable one out of the 10k controller ICs digikey has listed?

Thanks!

Why do you need constant current mode?

Primarily because charging time matters. CC mode is faster and also more efficient.

Use a step up converter with current limiting or a discrete constant current circuit.

Hi,
Although its an old analog IC, this may help you with your investigations.
LM317HVT
lm317hv.pdf (2.2 MB)

You could also Google;

regulated power supply module

There are power supply modules that have voltage and current regulation that you could set.

Tom... :smiley: :+1: :coffee: :australia:

For simplicity I'd use a voltage multiplier fed from a square wave. It works by charge transfer, so basically IS constant current.

Hi,
What is your application?
Are you trying to make a HIGH capacitance meter, using charging time constant?

Tom... :smiley: :+1: :coffee: :australia:

Nice idea but the desired current will result in a too high frequency or too big capacitors.

I don‘t need a final product, I‘m looking for an IC to build my own circuit which I could use for various applications.

One application in my mind is a battery powered spot welder.

An IC certainly is not usable by itself for your purpose. Look at application notes for buck converters which additional components are required.

Yes, off course I will need additional components. I‘m looking for an IC as the main component for a boost converter circuit, which works with 12V input voltage and delivers at least 0.5A of current.

I have no experience in power electronics and therefore I hope for some specific information regarding suitable components. From this point I think to have a chance to continue, but currently I‘m lost in choosing a suitable IC.

If you are too lazy to look into application notes then you can wait forever.

Maybe "ancient" MC34063? Up to 40 Vdc and (crude) input current limiting? I think you want constant input current to have constant power.
AN920 MC34063 DC DC converter app note.PDF (416.3 KB)

@ DrDiettrich

Believe me or not, I had a look at many application notes. I found interesting ICs, but not one which fullfills all requirements.
I had a look at: TPS61170, LM5155, LM2577, LM 2587, MC33063, LT1270, LMR64010. I also had a look at capacitor charge ICs such as LT3750. The latter is too expensive and the output voltage is "high voltage", which I don't need/want.

@ Smajadalf
I came across the MC34063. Voltage is ok, and it's cheap. It's beeing said, this IC is not suitable for sudden changes of the load. Don't know in detail what that means.

I don't need constant input current. I want to charge a capacitor and read that constant current is the way to do so, because it's faster and more efficient.

Can be faster. Always less efficient, because power is lost in the boost converter.

Then you missed the essential point, the parts around the IC. These are what makes up what is not covered by the bare IC.

@ jremington

Don't understand your point. If I wan't to charge to a higher voltage, there is always need for a converter circuit.
Capacitor charge at constant voltage is limited to 50% efficiency. This limit does not exist for CC.

@ DrDiettrich
I did not reach the point to choose diodes and inductors. Don't see how that makes sense, if I have not found a suitable IC yet?

Repeat as often as you like, it won't help :frowning:

Look at modules for LED lighting. They should be constant current in the appropriate voltage and current range, perhaps. 12V input boost supplies might be harder to find, though.

Note that ~40V output at 500mA is going to need close to 2A@12V input.

As an input I intend to use a 12V voltage regulated power supply.

Silly choice, if you have to add a boost converter. The entire concept is inefficient, pointless and the discussion a waste of everyone's time.

Ignored.