What If Your Onboard Chargers Have CAN Bus?

The OBC/EPS board uses a differential signal with two logic states to interface with the CAN bus on the vehicle's backplane. A CPLD manages the various digital interfaces to the OBC/EPS board. It then routes the data stream to the mission boards. The CPLD is programmed to be a voltage follower, which means the output pin logic level matches the corresponding paired input pin logic state.

The CAN bus is a low-level serial communication protocol that uses differential signals to communicate with various devices. To operate in a CAN network, a microcontroller with a CAN controller and a transceiver tied to the bus process a single-ended or differential signal. For example, a CAN bus sends the signal D+ low and returns it to the same level as D-.

A valid CAN frame is represented by two bits, called dominant and recessive. The dominant bit is the logical 0 and the recessive bit is the logical one. Nodes that receive a valid CAN frame will send a dominant message to the other nodes, which will acknowledge the transmission. If the receiving nodes receive a recessive message, they will send it back to the transmitting node. In this way, a CAN frame can be retransmitted until only one node remains transmitting.

A CAN message contains a message identifier, a number that is used to differentiate one message from another on the bus. The message identifier is 11 bits in length (Standard CAN) and begins with an identifier. After the message has been broadcast, each transmitting node compares the received value to the broadcast value. This process is called arbitration and ensures that no message will be lost.

CAN messages are created and sent by a node that is time-synchronized to avoid collisions. This node is known as a master node and a slave node. Each of these nodes can send or receive messages and can change the state of other devices on the bus. Today, many vehicles use a combination of two or more data buses.

CAN messages do not have an explicit address. CAN controllers intercept all traffic on the CAN bus and determine whether a message is interesting or not. Because CAN messages do not contain an address, they are referred to as "contents-addressed." Conventional message addresses would read "Here's a message for node X." In contrast, a contents-addressed message would read "Here's a CAN message containing data labeled X".

CRC is a process used to detect inconsistencies in a message. It is calculated based on a set of bytes of data and appended to an incoming message. The data receiver then evaluates the check value by using polynomial division to determine if there is an error. If there is, a negative acknowledgement is sent.

In CAN bus, this procedure is known as cyclic redundancy check (CRCR). It is used to detect errors and ensure reliable communication. Each message has a message identifier, called a message identifier. This number can be 11 bits for Standard CAN, or 17 bits for CAN FD. There are also recessive and dominant bits.

Cyclic redundancy check is a mathematical algorithm that detects errors and accidental changes in communication channels. CRC uses a generator polynomial that is available on both the sender and the receiver. The generated value is divided by a key that is available on both the sender and receiver. The remainder of the division is the checksum value.

CAN, or Controller Area Network, is the communication standard used by the automotive industry. CAN consists of a network of nodes, each of which communicates with the others. These nodes can share information from one part of the car to another. The data can be sent and received without loss.

CAN bus error handling reduces bus jamming by allowing a system to detect erroneous CAN frames and prevent further transmission. In addition, CAN nodes will automatically detect problematic CAN frames and change state accordingly. By doing so, CAN errors are prevented from propagating to other nodes and causing the bus to jam.

The CAN protocol is designed for high-speed communication between critical subsystems. Because of this, it needs to have high update rates and high data accuracy. CAN 2.0 was designed to meet these requirements. OBC's CAN bus supports a range of transmission rates from 8 Mbps to 1 gigabit per second.

Onboard chargers often use the CAN bus to communicate with the data network of the charger. In order to protect this communication line from electrostatic discharge (ESD) and transient voltages (ESV), the charger control unit must incorporate ESD and transient protection. In many cases, a single component can provide these functions. One of the most effective ways to achieve this is to use a dual-line TVS diode array. These diodes have minimal capacitance and do not degrade the transmitter/receiver I/O states.

An onboard charger is not a black box. In most cases, it is integrated with the battery management system and connected via the CAN bus. The design and structure of electric vehicles is complex, and the charger must fit into the design and interact with other electrical components. It is also possible that other electrical equipment on the vehicle may cause emissive and conductive disturbances.

When choosing an onboard charger, you need to decide what type of control you require. Summit Chargers are usually designed to support either an on/off signal or a CAN bus interface. Usually, these chargers are programmed to support only one of these methods, but you can easily reprogramme them to support both CAN and CANbus. For the best performance and safety, choose a charge algorithm that is close to constant current and a voltage slightly higher than the maximum pack voltage. This charge algorithm is designed to give you a back up in case the battery pack fails.