SMPS for Battery Charger 12v-150Ah

[prabhusweng]

Hi All,

I am creating a SMPS for the battery charger for the battery 12V-150 AH. This battery charger is for my home made inverter. The design for inverter is not yet started. Before that I want to finish the battery charger.

If somebody really interested please join with me.

Project specification:
Vin(low) = 180v
Vin(high) = 240v
Vin(nom) = 220v

Vout = 18v
Iout = 15A
Iout(min) = 1A
Efficiency 80%

Pout = 270W

So I have chosen the Half-Bridge topology for this project. Any suggestions are welcome. I am having the following components,
1. SG3525 / TL494 / UC3842 / UC3846 - Controllers
2. ETD 39 & 49 core.
3. IRF840 - MOSFET
4. MUR1560 - Diode

Is it possible to make this project using this components.

I want to have the following features in my project.
1. Input EMI filter.
2. Inrush current limiting.
3. Input transient voltage protection.
4. soft start.
5. simple startup method.

Regards
Prabhu

 

[DCPreamp]

That sounds like a cool project. But, it will present a fair amount of complexity. Still, I think you can do it with a circuit design very similar to a regular AC-DC, off-line SMPS. But, instead of using closed-loop feedback to keep a constant secondary voltage regardless of current, you will need to monitor both current and voltage.

So here's basically what your circuit could entail:
1) AC input, EMI filter, bridge, and large 450VDC filter cap
2) Balf-bridge primary switching (as you mentioned)
3) Switching transformer with appropriate winding ratio
4) Secondary rectifier and output filter cap
5) Current sense shunt-resistor (high-power, high-precision)
6) Secondary feedback circuitry that monitors both charging current and voltage

What type of battery are you charging? Standard lead-acid? SLA? Depending on the battery chemistry, your charge voltage/current curves will be different. When I've built chargers for small SLA batteries, I use a constant-current, equal to 10% of the battery's AH rating. Then, once the battery nears full charge, the charger switches from constant-current to constant-voltage. I've only built chargers for batteries up to about 10AH, so I was able to use an LM317. But for your design, you're looking at a lot more current, plus using the primary of the transformer, PWM'd to adjust the secondary, to give you your charging function.

Do you know exactly how to charge the battery? % of the AH rating similar to my small SLA batteries? You will need to do some research to fully understand what charging curves are ideal for your battery.

Attached is a schematic of a basic 250W AC-DC off-line SMPS with a half-bridge primary driver. It is designed for 230VAC in and uses a TL494 - also as you requested. It does use primary sensing for closed-loop regulation, but it certainly could be modified for secondary sensing to suit your needs.

I hope this helps a bit to get you started!

 

[DCPreamp]

Bad attachment

Wow, I just saw that only a thumbnail pic was posted. I attached a full-sized pic, but it didn't work. Sorry about that! Let me try again...

Turns out it was a .png file and the forum uploader didn't like it, so I converted it to a .pdf and it should be MUCH better.

Enjoy!

 

[prabhusweng]

Thanks for the circuit.

Yes it is little bit complex. But I have few ideas. In this case we don't need the closed loop control for either voltage or current. Instead we can have the simple SMPS without control loops. Latter at the output we can have the linear regulator for constant current and constant voltage. I agree this not efficient but we can reduce the complexity in the SMPS circuit. We can have the headroom voltage of the linear regulator as low so that we can reduce the losses in the regulator.

I am going to use tubular lead acid battery. Yes as mentioned I also have some experience in building CC/CV for small Lead Acid battery.

Now I am trying for bigger battery.

Following is the charging profile I planned to use.
1. Constant current of 10% of AH
2. Constant voltage (13.6V) after the current reduces to 0.5 A

Is this approach will work? If not we can discuss.

Now I am going to start the design of the circuit. Soon I will post the circuit.

 

[DCPreamp]

Sounds like you have the concept locked-down and have already weighed the pros-and-cons. That's great! Yes, I think it will work just fine, and even though the linear charger will be more complex, it will be offset by the simplified SMPS primary.

For the linear CV/CC circuits at fairly high power levels, check out this post: http://www.diysmps.com/forums/showthread.php?243-LM723-Based-bench-PSU

In that thread, I posted schematics for some big Astron linear power supplies rated at 0-15VDC and 0-50ADC with adjustable CC/CV. They are based on the ubiquitous LM723 and some serious series-pass transistors. I think these designs would be ideal for linear charger portion of your planned supply.

Great job, and I look forward to seeing your next post and circuit designs!