How to use the Power Path Selector function of BQ24170 with BQ3050?

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How to use the Power Path Selector function of BQ24170 with BQ3050? [Copy link]

Problem statement:

BQ3050 battery management packages the battery. There is only one Pack+ and Pack-. How to select the power path?

Assuming that the power path management function is not needed, should the Vbat and System (VSys) of BQ24170 be connected directly together?

The product function does require this function, so that it can directly receive power when plugged into the power socket.

If we connect Pack+ to the VBat of the circuit, and connect all the outputs of the system to VSys, however, the current of our system is relatively large (the maximum design value is about 15~20A), so I wonder if Bq24170 can be used in this way?

How does this place operate?

兰博

What is the answer from the host? I am looking forward to it.

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answer:

The understanding is correct. According to the architecture on the first floor, power path selection can be achieved. The sys in the circuit diagram refers to all system loads, that is, all loads that need to be directly powered by the battery when the charger is not plugged in.

If the system load current is large, the power of several MOSFETs in the power path selection circuit must be large, and the layout should take into account the influence of parasitic inductance of devices and traces. If the equivalent input capacitance of the system load is large, the conduction speed of the ACFET should be slower.

Question 2:
If I don't need this function, and my scenario is a 3-cell battery, can I refer to the 1-cell idea in the manual and remove the related MOS tube? The bq3050 has this charge and discharge control. It seems a bit redundant? Or, we want to reduce costs. Can this powerpath be omitted?

The system load in this project is too large, and the upper tube inside the BQ24170 cannot bear it, so you cannot connect it according to the 1cell idea.

Generally speaking, if the sum of the system load and the charging CC current is less than 80% of the mosfet peak current limit, then you can connect it that way.

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Since the BQ3050 has charge and discharge protection, it is only a protection function, but it cannot automatically adjust CC CV, because most high-series cells use switch-mode chargers such as BQ24170 , and the CC CV process requires the switch-mode charger to switch different control loops to achieve. Therefore, the charging protection function inside the BQ3050 can ensure the safety of the battery cell no matter what happens in the outside world, such as charger damage, load short circuit or other situations. This is necessary for high-series batteries. However, the BQ3050 cannot replace the charging mode adjustment function of switch-mode chargers such as BQ24170 .

Question 3

Michael, does this power path still need to be increased?

In this project, an external power path is required to achieve large load current. If the circuit related to BQ24170 is used , the mosfet inside BQ24170 will exceed the maximum peak current limit.

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Question 4 Another question from Michael.

According to the design of this power supply, the power of the power adapter should be equal to the charging power plus the system load power. This is relatively large, and a large power adapter is required. So, if you don't want to change the adapter. In this way, when both charging and system load are working, if the current is insufficient, should charging or output to the load be prioritized? If you want to output to the load first, then when the system load current is small, normal charging can be performed. Is this process controllable by the chip?

BQ24170 has a DPM function. When the input current reaches the maximum current limit, it will give priority to meeting the load demand. At this time, charging only uses the remaining current after meeting the load demand.