Let’s learn and analyze the circuit analysis of Changan Deep Blue Automobile’s BMS control panel (Part 2)

2023 is coming to an end soon, and this article should be the last of the year; everyone is busy at the end of the year, so let’s not go into details and get started.

Today we continue to study the BMS control board used in Changan Deep Blue Automobile; the functional module division of the entire circuit of this control board is roughly as shown below: only the key modules are marked here, which can be divided into two major circuit modules: high and low voltage. Among them, the high-voltage circuit module has High-voltage sampling function, insulation detection function, as for the current detection function, I couldn't find it at a glance; the functions in the low-voltage circuit module are also relatively general, such as communication, power supply, MCU, storage, etc. The power supply circuit includes several power chips, this Take a closer look at the back.

The key device models on the T side of this control board are listed as follows: The selected devices are mainly from major foreign manufacturers. There are 2 CAN channels and 2 redundant daisy chains. The daisy chain is an NXP solution and the microcontroller is also from NXP. , but there is no SBC with NXP.

The B side of the control board is as shown below. There are not many chips here. It is also found that there is a CAN transceiver on the B side, so there are 3 CAN channels in total.

The electrical structure of the entire control board is roughly as follows. I believe that there must be many incompleteness and errors in the drawing. It would be good for everyone to learn and understand its design concept, especially the high-voltage sampling circuit part. In fact, there are two connectors on the high-voltage module. There are 5 signal inputs. Because I don’t know the specific definition, the drawing here is inaccurate; the characteristic of high-voltage sampling of this control board is that there is no ADC or AFE placed on the high-voltage end, but the high-voltage signal is collected through the low-voltage side, and the high-voltage signal passes through the resistor After dividing the voltage, it is connected to the ADC inlet of the low-voltage end. Many optical MOS switches are used here, which are omitted in the following picture .

Next, let’s look at a few separate places. First, let’s look at the topology of the power supply. There are quite a few power supply chips on the board. The general architecture is as follows: The core power supply of the MCU is not shown. Note that there is a negative power supply that supplies power to the op amp.

Then take a look at this SBC chip TCAN4550-Q1. It is not an SBC in the usual sense. It integrates a CANFD transceiver and a CANFD controller internally. The interface with the MCU is SPI, but it has relatively few external power supply rails.

The specific application circuit is as follows, so the reason why this TCAN4550-Q1 is used here may be the CANFD function requirement, and this MCU does not support the CANFD controller function internally, so it needs to be implemented externally.

Next, look at the high and low side driver chips. This board uses 2 L9026 from Infineon. There are 8 channels in total, 2 of which are fixed as HSD, and the other 6 can be configured as LSD or HSD. If you are interested, you can find it Specifications, I have never used this chip.

Finally, let’s look at the high-voltage sampling circuit. The T side is an optical MOS switch, and the voltage dividing resistor is on the B side, as shown below: There are two types of resistors, one is a 1206 package chip resistor, and the other is a cylindrical type resistor. This resistor It should be to improve surge resistance.

Summarize:

I caught a cold again over the weekend and it was really uncomfortable. It has been a bit slow to sit down and write these two nights; all the above are for reference only.