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The fourth article in the energy storage series; the entire series is estimated to have 20~30 articles;
Through the previous articles, I have an understanding of energy storage, energy storage batteries, energy storage battery management functions and specific energy storage wiring;
Today we look at the circuit diagram of the two-wheeler lithium battery management system, and then do some analysis;
The following figure is based on the circuit diagram of Zhongying SH367309; as a whole, it is divided into the battery interface circuit on the left, the temperature sampling and charge and discharge protection on the lower side, the communication on the right side, and the sampling on the upper side;
If you correspond to this block diagram, you will have a better understanding of the functions of each circuit.
+PCB layout diagram
1. Voltage sampling and filter circuit
The following are the characteristics of the ADC used for internal sampling of the SH367309. It can be seen that the Sigma-Delta type ADC is used, and the sampling rate is very low, 10Hz;
There may be doubts here, won’t the series voltage of the top battery be 48V or above? ADC can withstand such a high voltage;
Quick answer first, here involves the concept of common mode voltage and differential mode voltage, the ADC input channel will actually select the upper and lower terminals of the battery as the input, so the input voltage of the ADC is the battery voltage
Do not expand further;
2. Current sampling circuit
The following R35/37/40/42 are sampling resistors, which enter the current sampling terminal of RS1/RS2 of the chip after passing through the filter
The following is a photo of manganese copper, there are also called shunts, the resistance is low, and the current that can pass through is large;
R35/37/40/42 are 5 milliohm resistors connected in parallel, which is 1.25 milliohm;
If calculated by 20A current, the resistance voltage is 25mV; if the current is 100mA, the voltage is 0.125mV (125uV);
This requirement for current sampling ADC is still high, it can be seen that it is a 16bit ADC
3. Charge and discharge control and protection
As shown in the figure below, you can see that the two N-MOSs of Q2 and Q3 are connected back to back (drains D are connected together); one consideration for why this is done is that there are parasitic diodes inside the MOS, in order to ensure absolute control. control;
4. Other circuits
Injection temperature collection, battery voltage collection, and communication with the main control MCU can be analyzed from the figure;
The next article will introduce some core parameters of AFE;
For the SH367309 information referenced in this article, you can follow the official account and reply "SH367309" to obtain
Welcome to pay attention to the official account and go deep into the chip industry chain together;
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