2kW Li-ion battery charger

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Chandrasekaran
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Hi Infineon,

I am working on a 2.5KW battery charger and I have gone through the Application note of the Evaluation Board (2KW EVAL_2kW_48V_CHAR_P7) a Lead-acid/Li-ion battery charger of Infineon. 

https://www.infineon.com/dgdl/Infineon-Applicationnote_EVAL_2KW_48V_CHAR_P7_2kw_battery_charger_Cool...

Here are my queries.

There is a resistor (R200) across the capacitor (C90) in the schematic but in the evaluation board that resistor is not present. But when I checked the current version of the schematic the capacitor C90 is not present. Can you explain this variation in schematics?

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1 Solution

Hi @Chandrasekaran ,

The BMS signals, together with the corresponding hardware circuitry (R159/R160...&Q12/Q17), make up the Li-ion battery wake-up function of the 2KW EVAL_2kW_48V_CHAR_P7 charger.   Note that the wake-up function is only active in Li-ion mode, it is not active in lead-acid mode.

To better understand this circuit, it is good to have some background information on why modern Li-Ion batteries go into sleep mode, and the following URL gives a nice summary:

https://batteryuniversity.com/article/bu-808a-how-to-awaken-a-sleeping-li-ion

In order to recharge a lithium-ion battery that enters sleep mode, the lithium-ion battery's protection circuit (or BMS) must to unlock the battery cells and reconnect them.  This can done by several ways,  for 2KW EVAL_2kW_48V_CHAR_P7 charger, we use the nominal voltage supply method ( power on a nominal voltage at the battery connector) to reactivate the battery for starting a normal charging process.

However, noticed that the battery charger is not designed for open load operation (it is not a traditional regulated power supply), this leads to oscillations in the output voltage and further leads to the possibility that the BMS system of lithium-ion batteries may never be able to reconnect the battery cells.

Therefore, a dummy load should be added, capacitors used to be a good choice (C90), but in some cases users would observe electrical sparks when connecting the battery. This is why we substitute capacitor C90 for resistor R200.

During the wake-up function phase, the XMC controller enables Q12/R200 to keep the output voltage at a specific value. When the Li-ion battery is successfully woken up and enters the charging mode, Q12/R200 is disabled to minimize unnecessary power consumption. From a product performance perspective, we do not recommend that you remove the BMS control signal.

For more information about the behavior of the EVAL_2kW_48V_CHAR_P7 's wake-up function, please refer to the source code we provided. As these are unpublished information, it is no longer appropriate to continue the discussion in the forum, thank you for your understanding.

Kind Regards,

Neo

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Neo_Qin
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Hi @Chandrasekaran ,

Thank you for considering Infineon for your design collaboration.

According to the description of the "Revision history" section, it looks like the R200 is the actual mounted device.

Neo_Qin_0-1702790451985.png

Kind Regards,

Neo

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Harrykapki
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First reply posted Welcome!

The variations exist between the schematic and the evaluation board of the 2KW battery charger from Infineon, specifically regarding the presence of resistor R200 across capacitor C90. Such differences in schematics can arise due to design iterations, changes in component availability, engineering corrections, or application-specific configurations. The absence of R200 in the evaluation board might signify that the design has evolved, and the latest version may not require this component for its intended functionality. 

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Chandrasekaran
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Thank you for the reply,

I'm planning to remove the entire section of the BMS signal (I.e R159, R160, R173, R175, R200, R161, R162, R163, R164, R165, Q12, and Q17) instead I'm gonna add a power resistor between bat+ and bat-

Is this okay? 

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Hi @Chandrasekaran ,

From a hardware perspective, this is similar to a passive balancing circuit, which used to balance battery voltage, discharging batteries with higher charge until all individual batteries have equal charge.

The BMS signal finally routed to the P4.1 pin of the XMC controller, and I am reading the source code to confirm what function this circuit is. Once I have a definite answer, I will get  back to you ASAP.

Neo_Qin_0-1703423234939.png

 

Kind Regards,

Neo

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Chandrasekaran
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Thank you Neo for the reply,

Awaiting your feedback.

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Hi @Chandrasekaran ,

The BMS signals, together with the corresponding hardware circuitry (R159/R160...&Q12/Q17), make up the Li-ion battery wake-up function of the 2KW EVAL_2kW_48V_CHAR_P7 charger.   Note that the wake-up function is only active in Li-ion mode, it is not active in lead-acid mode.

To better understand this circuit, it is good to have some background information on why modern Li-Ion batteries go into sleep mode, and the following URL gives a nice summary:

https://batteryuniversity.com/article/bu-808a-how-to-awaken-a-sleeping-li-ion

In order to recharge a lithium-ion battery that enters sleep mode, the lithium-ion battery's protection circuit (or BMS) must to unlock the battery cells and reconnect them.  This can done by several ways,  for 2KW EVAL_2kW_48V_CHAR_P7 charger, we use the nominal voltage supply method ( power on a nominal voltage at the battery connector) to reactivate the battery for starting a normal charging process.

However, noticed that the battery charger is not designed for open load operation (it is not a traditional regulated power supply), this leads to oscillations in the output voltage and further leads to the possibility that the BMS system of lithium-ion batteries may never be able to reconnect the battery cells.

Therefore, a dummy load should be added, capacitors used to be a good choice (C90), but in some cases users would observe electrical sparks when connecting the battery. This is why we substitute capacitor C90 for resistor R200.

During the wake-up function phase, the XMC controller enables Q12/R200 to keep the output voltage at a specific value. When the Li-ion battery is successfully woken up and enters the charging mode, Q12/R200 is disabled to minimize unnecessary power consumption. From a product performance perspective, we do not recommend that you remove the BMS control signal.

For more information about the behavior of the EVAL_2kW_48V_CHAR_P7 's wake-up function, please refer to the source code we provided. As these are unpublished information, it is no longer appropriate to continue the discussion in the forum, thank you for your understanding.

Kind Regards,

Neo

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Chandrasekaran
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Thank You, @Neo_Qin for your explanation and support.

I've one more query since I'm increasing the output power from 2Kw to 2.5Kw. I just want to know your recommendations for the hardware changes that need to be done in the PFC section. 

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Hi @Chandrasekaran ,

Unfortunately, it seems we don't have a dedicated design calculation document available for the dual-boost converter.

Provided that the output voltage remains the same, I think it is currently most convenient to refer to the BOM in 3kW EVK:

EVAL_3KW_DB_PFC_C7_2

Considering that dual-boost is very close to the conventional CCM-PFC from the point of view of device parameterization, you can also use the AN: Design guide boost type CCM PFC with ICE3PCSxx   as a reference.

Kind Regards,

Neo

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