Circuit design of EPB parking current acquisition node system based on CAN bus-EEWORLD

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　　The electronic parking brake system (EPB) refers to a technology that integrates temporary braking during driving and long-term braking after parking, and realizes parking braking by electronic control. In order to obtain the theoretical parking pressure applied by each vehicle, monitor the working status of the integrated actuators of each vehicle, prevent the parking motor from working in a high current state for a long time, and prevent the parking motor from overheating and burning, the EPB is generally equipped with a parking vehicle current acquisition node, and sends the parking current to the central control node (ECU) through the CAN bus. This article mainly introduces the interface setting of the parking current acquisition node based on AD574A.

　　1 System Hardware Design

　　The hardware circuit design of the parking current collection node includes two parts: CAN bus communication circuit design and vehicle speed collection circuit design, as shown in Figure 1.

Circuit design of EPB parking current acquisition node system based on CAN bus

　　1) CAN bus communication circuit design

　　When designing the CAN bus communication circuit, the CAN controller used is CTM1050T and the microcontroller uses AT89S52.

　　2) Current acquisition hardware design

　　Current sampling is performed through AD574A, which is a 12-bit high-speed successive approximation analog-to-digital converter, which is very suitable for use in high-precision fast sampling systems. For the acquisition of parking current, considering that the direction of parking current can be changed in order to control the direction of motor rotation, AD574A bipolar input is used, which is divided into 8-bit and 4-bit outputs.

Reference address：Circuit design of EPB parking current acquisition node system based on CAN bus

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