Car battery charger

[arash_tah]

Hi friends
I want to build a 50A 13.6V switching charger for car battery
Does anyone have a good schematic and dsesign

[vanko]

I'm interested in this too. All Ideas are welcome.

[arash_tah]

I can build this charger using iron transformer but it would be very bulky and heavy therefore I decided to use high frequency transformer (ferrite) I think half bridge or two-transistor forward topology is suitable for mu application. Does anyone have any experiance in this area?
please help me.

[tAhm1D]

Hi,
Yea, I'd go for half-bridge instead of forward. Okay, firstly choose your controller (most common is SG3525), then your high/low side MOSFET driver (you could use IR2110/IR2113). Do your calculations for the transformer (this is the most important part of the converter). Decide on your output stage (Schottky/Ultrafast/Synchronous) and the output inductor, your feedback loop. Decide on your input stage (rectifier + filter). Then your battery monitor (voltage and current). This could be done with an opamp and discrete circuitry, although I'd do this with a PIC(or any microcontroller you know). This is all in brief, although implementing this in real life isn't as easy as it sounds though. When you decide on all these parameters, post them here, so maybe I can help you further. (It took me one year before I could confidently and successfully build SMPS circuits).
But before this, a background knowledge of SMPS is VERY VERY important. So, I suggest you read through Marty Brown's Power Supply Cookbook for a month or longer before deciding to go SMPS (that is if you haven't done so already).
Hope this helps.

[SFx]

you can use power suply from PC

[oldvan]

...I want to build a 50A 13.6V switching charger for car battery...

you can use power suply from PC

Problem: 
12.0 < 13.6
How to work around this?

Possible to use three matching 5V 50 Amp switching power supplies in series, provided
their output is isolated safely and the voltages can be adjusted down to 4.53V each.

[arash_tah]

HI tAhm1D  I am not beginer in this field I have read Pressman's book and I have some softwares for SMPS designing  I also have designed a flyback and buck converter with low and medium power But what I am going to have is a schematic and complete design to start with of cource I need to make some changes to make them suitable for my application. I want a starter design! When I complete my design I will share with others in this forume. Do u have any starter?

To Sfx computer power supplys  are low power and their voltage is not in the range of my desired voltage on the other hand they are designed for computer and have no protection against overload and other unwanted condition so they are not apropeate for harsh application like I want

Posted on: January 03, 2010, 06:41:15 06:41 - Automerged
HI oldvan  u are right 12<13.6
using 3  5V computer power supply is good idea but as I said computer power supply are not apropeate  for harsh condition they have no current limit facility. for a battery charger current limit is very crucial feature that we cant neglect it.

[fikus]

http://www.elitesecurity.org/t370885-1#2347793
Red color in sch is need to change or build new.
If you need a translation, ask...

[arash_tah]

Hi fikus tanx for your reply
Can u tall me aome detail about this circuit? I what dos it do?
the rea section is added to atxpower to change it into battery charger?

[tAhm1D]

Hi arash_tah,

HI tAhm1D  I am not beginer in this field I have read Pressman's book and I have some softwares for SMPS designing  I also have designed a flyback and buck converter with low and medium power But what I am going to have is a schematic and complete design to start with of cource I need to make some changes to make them suitable for my application. I want a starter design! When I complete my design I will share with others in this forume. Do u have any starter?

I see. So you won't face that much difficulty in finishing the half-bridge design.
As a starter, take a look at the attachment.

[fikus]

Yes, it's ATX power supply and revised to charge 12v battery. Biggest job is rewind the transformer.
The primary side of transformers remain, the secondary winding is only for 12V (13.8V).

[arash_tah]

Hi tAhm1d good design
But there is some thing wrong!!
Is the output of this power supply regulated?
How does the feed back work?
Loop gain is extremely high and this will lead power supply to unstability
are u sure it works withno problem?


Posted on: January 04, 2010, 02:29:43 14:29 - Automerged
By the way there is no current limit cicuitry
Do u have any idea for this purpose?

[tAhm1D]

Yes, the output is regulated through feedback. Since the output voltage here is very high, a shunt regulator like TL431 could not be used, so zener-opto isolated feedback is used in the circuit. Yes it is working fine. Although for your requirement, ie 13.6v, you should use TL431 or something equivalent for better feedback control.
For current limiting, you could use current transformer which is most common in half bridge design, placed between the ferrite transformer and the point where the high side source and low side drain meet. (see attachment) Then through necessary circuitry, sense the voltage at the transformer secondary.
Another possible way is to use a shunt resistor between the low side source and ground and sense the voltage drop across it.
Both ways should work, whereas mostly I have seen the usage of current transformer in half-bridge designs.
To shut down the PSU, you can do two things:
1) Pull SG3525 pin 8(Soft-Start) low when overcurrent is detected
2) Set SG3525 pin 10(Shut-Down) high when overcurrent is detected
This is done for overcurrent protection, ie, turning off the PSU when the load requires a current greater than your maximum limit. Another thing that could be done is instead of shutting off the PSU, you could reduce the voltage by reducing the duty cycle, in turn reducing the output current and bring it within acceptable bounds.

Posted on: January 04, 2010, 03:24:58 15:24 - Automerged
P.S. In half-bride circuits I almost always use hi/lo side driver ICs, although in some places, I have seen people having difficulties with these chips. In such a case, you could use pulse transformers instead.
If you go through Marty Brown's Power Supply Cookbook, it will be very beneficial for you as everything, starting from control circuitry to power stages and current sensing, feedback and other control techniques are quite well explained. Furthermore, there are two projects with half-bridge design given at the end, which will be helpful.