voltage and current regulator? 3~48V @ 0.1~10Amps

[dingbatca]

Working on a battery charger. Using a PIC for a brain. As far as I can tell I only need two parts to make a battery charger. A current and Voltage regulator. From there I can get any desired output.

I need help on finding the components. I need a voltage regulator that can go between 3~48V and a current regulator that can go between 0.1~10Amps. 48V 12A input.

Can I do this with one part? Should I use two different parts? should I build it all from scratch? ideas?
-DingbatCA

 

[kchriste]

If you are going to use a PIC, use a PIC30F1010 or PIC30F2020 which is designed for power supply use. Then add some code, FETs and FET drivers, etc and you have a switching power supply.

 

[dingbatca]

Would love to, but... My compiler is only good on the 16 and 18 series. I was figuring I could use a single mosfet for voltage regulation, but I have no clue how to build a current regulator.

 

[kchriste]

You can still do it with a 16F or 18F except the switching frequency will be lower. Find a PIC with the highest PWM clock frequency. For current regulation you simply use a shunt resistor to measure the current and add it to the control loop. There are battery charger chips out there designed for different battery chemistries but for 48v you'll probably have to roll your own. You don't have to use a PIC unless you want to for some reason.

 

[dingbatca]

Looking to charge NiCD, NiMH, Lithium-Polymer/Ion/A123 and PB. I would would like to do that in one box. I was thinking two control loops, one for voltage and one for current. Does that sound right?

 

[Hero999]

You could do that if you like but you can't regulate both the voltage and current at the same time.

 

[dingbatca]

Can I use two different circuits to allow me to regulate both at the same time?

 

[Hero999]

Yes of course you can I was thinking about doing both to a single circuit.

 

[Nigel Goodwin]

Yes of course you can I was thinking about doing both to a single circuit.

I think he's confused you!

Of course you can't regulate both - ohms law applies at all times.

 

[kchriste]

As mentioned, you can't regulate both current and voltage at the exact same time. However, you can still have two control loops; one voltage and one current. The way you set it up is to have one dominate the other. Usually the current loop dominates by putting an upper limit on current flow. For example, in a lead acid battery charger, the current control loop will limit the current until the voltage rises to the charge termination voltage. Then the voltage control loop kicks in and maintains a steady voltage as the current decreases due to the battery being unable to absorb any more charge. Once the current drops to a certain level, then the voltage loop set point is updated to a lower voltage to maintain the battery charge level (float voltage) as the battery is fully charged. What I just described is called a 3 stage charger.

 

[dingbatca]

kchriste, that is EXACTLY what I am looking at doing . I know how to build a voltage regulator using a mosfet and PWM from the PIC. I do not know how to build the current regulator. I am happy with a single chip solution, but other members we kind enough to point out that for my power/voltage levels I may have to build my own. Any ideas on this matter? 3~48 volts and 0~10 amps, or close.

 

[neon]

Working on a battery charger. Using a PIC for a brain. As far as I can tell I only need two parts to make a battery charger. A current and Voltage regulator. From there I can get any desired output.

I need help on finding the components. I need a voltage regulator that can go between 3~48V and a current regulator that can go between 0.1~10Amps. 48V 12A input.

Can I do this with one part? Should I use two different parts? should I build it all from scratch? ideas?
-DingbatCA

Simple lm117 now to get 48 vyou need two in series and make sure the division is 24v each. you nwill also need transistor bypass for the current of 12A. PWM can also be used but not as easily as lm117.

 

[Hero999]

This is how you can modify a constant voltage regulator for constant current operation.

https://www.electro-tech-online.com/threads/best-way-to-power-a-white-led.30656/#post227445

You'll need to tweak this a bit and use a regulator rated for 10A.

Also what are you going to use for the power supply?

You can buy a 48V SMPS but you need more than that to account for the dropout voltage. Fortunately most 48V power supplies can be tweaked to well over 50V.

Finding op-amps that will take such a high voltage might also be a problem unless you use low side sensing or a hall effect current sensing.

 

[kchriste]

I know how to build a voltage regulator using a mosfet and PWM from the PIC. I do not know how to build the current regulator.

Look into the INA168, or other current shunt monitor IC, which will convert a highside current (when used with a shunt) into a ground referenced voltage. The INA168 will work up to 60V. All you need to do is feed this voltage into the 2nd ADC input on the PIC and use software to decide which loop (current or voltage) will dominate at any one time. Use a pseudo (Or a real one if you are up to it) PID control loop to maintain stability of both PWM control loops.

 

[Speakerguy]

For high-side current sensing I highly recommend the MAX4080:

**broken link removed**

IMO it would be ideal for your requirements.

 

[dingbatca]

I think at this point I need to write some code and build up all the basic components. Thank you all for the great responses.
-DingbatCA

 

[neon]

I think at this point I need to write some code and build up all the basic components. Thank you all for the great responses.
-DingbatCA

Sorry what do you expect. Every body give you their version of the bible as they understand.

 

[b rett2010]

Quite a requirement ... It won't meet all your specs but the LM338K (TO3) can handle high curents at over 30V. It doesn't answer your requirement fully, but it is a hell of a regulator supplying 32V at up to 12A (heatsinked and I'd use a fan). But - it can be used at higher voltages - everal hundred when floating, so you could reach your voltage using this technique.

Check out the datasheet - I'm unsure how well floating the regulator would respond to the battery. Just an idea ... I'm working with some at the moment so they came immediately to mind. I don't know enough to advise you further than pointing this out.

 

[podgymax]

how can make two lm117 in series? Can anyone draw it for me?