TL494: TL494

Hi,

What is your input voltage, and charging current? I assume your battery voltage is 48V.

For constant voltage and constant current charging (CVCC), can you look at UCC28740, UCC28704 which have integrated features of CVCC.

Hi,

The input voltage is 55V DC and charging current is 20A. The battery pack is 48V as noted by you. I have tried to create the schematics by studying the components on the board. The same is copied below / attached (charger.jpg).

1. I like to know if the below circuit serves as a charger for the LiFePo4 battery.

2. Does it take care of both constant current and constant voltage charging needed for the battery?

3. Can you suggest a reference design for charger using the above input and output specifications - either based on TL494 or other controller. 

Hi,

1. The circuit shows L1 and L2, and when M1, 2, 4, 5 conduct, the current direction is as shown by two red arrows. When M1,2,4,5 turn off, L1 and L2 do not have free wheeling path. So it looks this circuit does not work

2. I cannot tell, unless you provide the detail of how feedback is made.

3. Can you please first reply to the above? 

Hi Hong Hung,

corrected freewheeling diode path in attached drawing. We also added MOSFET card blocks to get better understanding .

Can you please help to get your feedback.

/cfs-file/__key/communityserver-discussions-components-files/196/Reactifier-block_5F00_updated_5F00_20200704.pdf

Hi Hong Hung,

As Arumugam updated, the freewheeling diode is marked now in the block diagram. But we are still working on tracing the feedback path and will get back to you soon. Apart from this if you have any other questions, please let us know. We are in the process of re-engineering, the circuit is being drawn by tracking components on board. We do not have complete schematics of this design yet. 

Outside this design If you have any solution for CC/CV charger circuit that meets our requirement, please share the reference design.

Regards,

Manjunatha.

Hi Hong Hung,

The feedback path of the TL494 is given below diagram. Please share your feedback.

/cfs-file/__key/communityserver-discussions-components-files/196/Reactifier-block_5F00_updated_5F00_20200705.pdf

Hi,

I have two questions:

(1) U11 is go to current limit but I cannot find where U11 is connected to a current limit control circuit. Can you help indicate where U11 is connected and where is the current limit circuit?

(2) I assume B+ and B- are your 48V output terminals. But your circuit shows TL494 feedback from +12V_A, which is to use TL494 to regulate +12V_A. But I cannot find how 48V (B+ and B-) is regulated from +12V_A. Can you describe how 48V is regulated by TL494?

Hi Hong Hung,

Thanks for your reply.

Please find below our answer and attached updated block diagram.

1. Yes your assumption is correct B+ and B- is Battery terminal, From our understanding +12V_B is used for feedback control of the TL494 through opto coupler. We believe +12V_B indirectly controlling the TL494 output mosfet (48V)

2. U11 is not current limiter but it’s a regulator which supply power to the Gate Driver. Apologies for the confusion. 

Please confirm our understanding is correct ? whether this circuit will comply the CC/CV charging operation ?

/cfs-file/__key/communityserver-discussions-components-files/196/BMS-Charger-and-switching-board_5F00_TI.pdf

Thanks and Regards,

Arumugam.P

Can you describe how +12V_B can control 48V regulation?

How is your constant current control is achieved?

Hi Hong Huang

We are clueless on this. Hence we are seeking your inputs. We have drawn this schematics diagram by tracing the components on PCB. This unit is supposed to be part of a battery management solution.

We suspect this portion of the circuit - TL494 in combination with UC2843 to be the CC/CV charger solution. We need your help to understand this circuit better. Can you please share your inputs on this?

Do you have any other reference design that can do CC/CV charging? Please share details.

Regards,

Manjunatha 

Hi,

Can you also show the circuit of UC2843?

I do not have a reference design for 57V to 48V CC/CV. If you need such a reference design, please talk to your local TI sales and ask to help request a reference design for you.

Hi Hong Huang,

A high level circuit is added in the pdf already. Please check if this is good enough.

BMS Charger and switching board_updated.pdf

Regards,

Manjunatha

HI,

I do not see UC2843 circuit in your updated. Before you show clearly how 48V output can be regulated in constant voltage and constant current in the circuit, I cannot comment if this circuit ok or not.

Where did you get the circuit board can you talk to the designer directly?

Hi Hong Huang,

We do not have contacts with the designer. We have the board and trying to derive the circuit by tracing the components on board. So the circuit representation shown in out drawing may have errors. So we are seeking your help to identify the right circuit. Moreover we are not claiming that this circuit is CC/CV charger, but just speculating as this circuit is part of the battery charger system. The attached pdf is updated with some details on the UC2843 circuit. But once again we might have got it wrong or incomplete due to difficulty in tracing components on the board.

Please provide recommendations or refer us to a local FAE. We are based our of Bengaluru in India. May be you can help us with connecting with our local FAE. Appreciate your patience and support.

Regards,

Manjunatha

BMS Charger.pdf  

Hi,

We do not have an existing design that meets your specs. If you want to have a reference design for your application, please ask your local TI sales office.