What is the purpose of the CAN bus in power supplies? [GUIDA 2023]

In traditional power systems, the control of functions and monitoring of the state are achieved through some common modes.

The programming of the output voltage usually occurs using a source. external direct current.

The most common method to display the status is through the use of LED indicators, of the "Power Good" relay or signal"that inform the user or the controller that the output voltage of the power source is ready.

These methods satisfy the needs of most applications., but not all of them.

With the advancement of technology and automation, there is now an increased need to process more information about products simultaneously.

So this is where protocols come into play. PMBus and CAN bus; let's see the main differences.

PMBus Protocol

The power management bus (PMBus) communicates through commands using two bidirectional lines, Serial Data Line (SDA) and Serial Clock Line (SCL), which means it only requires three signal wires (including a GND wire) connected between the devices. For example, to achieve control and monitoring of the system with multiple power supplies, a control unit (master) can communicate with each power supply (slave) through the bus.

This method significantly reduces the volume of control and signal wiring, resulting in fewer circuit failures, greater system controllability, and simplified installation. The PMBus has been used in various fields, including industrial automation and telecommunications.

Advantage: Since the protocol is free, developers can easily incorporate PMBus into their systems.

Disadvantage: Low immunity to electrical interference, which makes it suitable only for short-distance communication.

Diagram of a PMBus

CAN Bus Protocol

The Controller Area Network (CANBus), which uses the differential reporting method (The input "CANH" doesn't appear to be Italian. Could you please provide a correct Italian sentence or phrase? and Your text "CANL" doesn't seem to be Italian. Please provide a valid Italian sentence or phrase.), was initially designed for the automotive industry to replace complex wiring. CANBus is becoming increasingly popular in a variety of industries, including production and automation systems, thanks to its high immunity to electrical interference and the ability to self-diagnose and repair data errors.

Advantage: Excellent resistance to electrical interference.

Disadvantage: Some power supply manufacturers (including Mean Well) they only define a part of the protocol for which modifications might be necessary during the implementation in the final system.

Diagram of a CAN bus National Synchrotron Radiation Research Center - CANBus

CAN Bus application example

Here is a 96 kW project from the National Synchrotron Radiation Research Center in Taiwan, where multiple sets of high power supply systems are used. The output of the power supply system is used to power clusters of solid-state radio power amplifiers, which generate high-frequency energy to accelerate electrons almost to the speed of light. To match the RF power required by the storage ring and achieve the best energy efficiency, the output voltage of the power supply system must be adjustable between 42 V DC and 54 V DC in the modulation range for each operating point with a specific RF power level.

Programmable power supplies with communication function not only they simplify control and monitoring complex, but they are all suitable for applications that require a intelligent control and monitoring.

Mean Well offers models suitable for various uses, including RSP-1600/RSP-2000 and DPU-3200 for general applications, RCP-1600/RCP-2000 and DRP-3200 for rack installations UHP-1500/UHP-2500, PHP-3500/PHP-3500-HV for fanless applications or water-cooled.

In-depth study of CAN bus

The system CAN-bus, known as Area Network Controller, represents a serial standard designed to establish connections between various electronic control units, such as sensors and control units. This standard, originally conceived in Germany in the 80s by the company. Robert Bosch GmbH, it found its first application in the automotive industry.

The distinctive feature of the CAN-bus protocol is its ability to operate in notoriously hostile environments, characterized by strong electromagnetic interference.

Currently, its use has extended to multiple embedded industrial applications, where the need to ensure significant resilience to interference remains a fundamental requirement.

The communication based on the CAN protocol is regulated by the standard. ISO 11898-1 (2015) and is structured in a data exchange level (data link layer) which, in turn, is composed of a "logical" layer named Logical Link Control (LLC) and a lower layer known as Media Access Control (MAC). Moreover, it is possible to add additional layers, such as "physical" layers, based on the needs and decisions of the network designer.

How does a CAN bus work?

You didn't provide a term to translate. Could you please provide the term or sentence you want translated?bus"It refers to a series of communication channels used for the exchange of data and information between devices and components within a computer or electronic system. A bus provides the ability to connect different devices to each other, using both a parallel transmission mode (such as ISA, PCI, AGP...) and serial (such as SATA, SPI, PCI Express, USB, PROFIBUS, CAN...)."

In the context of the CAN bus network, they are defined four distinct types of messages or frame, each with a maximum capacity of 94 bits and a specific priority (Arbitration Field).

• Data frame: These constitute the most common type of message and are used for data transmission. They are composed of various fields, including the arbitration field, the acknowledgment field, the data field, and the CRC field.
• Error frame: This type of message is special and is sent when a node detects an error during communication.
• Overload frameThese frames are very similar to error frames and are transmitted by a node when it becomes too busy. However, with the evolution of increasingly intelligent CAN controllers, this type of frame is used less frequently.
• Remote frame: This type of frame is uncommon and is usually used to request information from a specific identifier.

What are the advantages of the can bus protocol?

Its main advantages and its peculiarities are:

• ReliabilityThe probability of data loss during message transmission is virtually nil. Thanks to the various error detection options, the CAN-bus standard proves particularly suitable for applications that require a high level of security and robustness.
• Economic efficiencyThe reduction of weight, wiring, and production costs is the main objective behind the creation of the CAN-bus standard in the automotive industry. This simplifies not only the installation but also the maintenance.
• FlexibilityThe CAN-bus protocol is based on communication through messages rather than on the specifications of the devices in the network. This aspect allows the addition and integration of new electronic devices without requiring dedicated programming.
• SpeedThe sharing of real-time data between network nodes and the ability to process data in a shared manner give high speed to the entire network.
• EfficiencyThe ability to manage the priority level based on message IDs allows for a smooth and efficient management of various frames, ensuring the overall efficiency of the network.

Explore our selection of power supplies compatible with the CAN bus protocol!