BQ24450

Hello Pankaj Deosarkar,

Thank you for considering using Power Integrations Product.

Before we dig in, i want to learn the probelm better. What do you mean by "use BQ24450 charge controller IC on secondary side". do you mean the top switch provide the input of BQ24450?

Best Regards

Hello Sir

BQ24450 is a charger controller IC which takes DC input and provides modes like float,boost which improves battery life.

I didn't find any feedback pin in Bq24450 as TOP261EN needs feedback through opto. 

Can I use TL431 shunt regulator after BQ24450 so that I will get feedback as well as control over the charging modes.

I attached the schematic in which TOPSwitch not shown which is in primary side. I just tap +12V and operate with Opto is this topology going to work.

or do you suggest any changes.

Sir actually i want design calculation of smps using linkswitch CV in proper steps so that i understand how values of component will decide for perticular rating.

Better you try PI Expert tool , will give you values its rating and all rquired things, for calculation purpose refer notes on LInkSwitch family.

Hope you find this useful.

Hello Pankaj Deosarkar,

If i understand it right, what you need is a DC input for the battery Charge IC. i suggest you put the FB circuit of TOP switch before BQ24450. In this way, TOP swicth will give you a stable DC input. As i am not the expert for BQ24450, you should check the requirement of the input of BQ24450. if TOP switch can supply, it should be OK to use.

I don't suggest you put the FB circuit( TL431 shunt regulator you mentioned) after the BQ24450, As BQ24450 is smart battery charger, it should be able to control the output voltage and current itself. if you put the top switch loop here it will be two close loop together, it will make the system unstable.

Best Regards

Hello jagrutiraut3,

Thank you for considering Power intrgrations products.

Can you please open another new forum topic. in this way, it will not confuse the discussion.

Best Regards

Thank you for your reply. I will make this changes and try.

actualy i want to use lnk623 ic

Hello jagrutiraut3,

Please open another new topic to discuss. this is for  Pankaj. 

Best Regards

Hello 

I did same as per above suggestion, following are observations

1. Some noise is coming out of Transformer what will be the probable reason.

2. Also 15V secondary of transformer shoots to 40V 

any suggestions 

wht is the max current limit of feedback pin and what happen if limit would cross?

Hello jagrutiraut3,

In order to keep every forum clean and easy to track, please open another forum topic. 

I am not quite clear about you question. Can you put more details in the new topic such as shcematic, part number and applications. In this way, we hcan have a better understanding of your problem,

Best Regards

Hello Sir

I am using TOP261EN for 12V/10A battery charger. I came across TOP switch auto turn off when I am applying 10A load within a few seconds. I tried different heat sinks for that but no effect. What may be the reason for this. Any suggetion 

Hello Pankaj,

Is this still the same project you mentioned in this forum before?

Before we dig in, can you tell me more about the test conditions, like the input voltage? if possible, can you share the schematic with me?

Best Regards

Hello Sir

Yes for the  same above mentioned project. I just changed CCCV controller from BQ24450 to TSM101AIDT.  I attached the schematic.

Please go through it.

Hello Pankaj,

Sorry for the late reply. I went through your schematic and put it the PIxls spreadsheet. There is a warning about over load curreny ratio at vMIN. you can also use the online spreadsheet to do the same check. Below is the link.

https://piexpertonline.power.com/site/login

May I ask if your problems only happen at low line 85VAC or it happens at all input voltage like 230VAC or 165VAC?

By the way, how much turns ratio is your transformer designed? I need this information to do the calcualtion of how much your currnt limit reduction factor is needed.

Best Regards

Hello Sir,

My problem was with 230VAC.Right now I didn't tested it with 90VAC. NP:NS = 9.024 for 15V.

Also I heard some noise about of 100Hz from transformer when output is shorted. 

Hello Pankaj,

I checked your design of the power supply part, it looks OK for me. The only blank part is the trasnformer design. Did you use our PIxls design tool to do the design or something else, can you please share the PIxls or transformer design with us?

you mentioned at 10A the power supply will turn off, how much load it can work normally, 5A, 8A?

If possible, can you also share the layout file.

Best Regards