ADM1041: Intelligent Integrated AC/DC Power Supply Controller-EEWORLD

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Most semiconductor manufacturers often overlook the integration of the secondary side of AC/DC redundant power supplies, resulting in numerous discrete components such as operational amplifiers, transistors, resistors, capacitors, and digital logic circuits that perform various secondary monitoring functions.

A recent addition is the need for more communication between the power supply and the rest of the system. The trend toward intelligent power supplies with digital interfaces is now becoming a standard requirement for most new designs.

There are some devices on the market that have some level of integration, such as current sensing, voltage sensing or OrFET control, but all require a lot of external circuitry, a microcontroller and an electronically erasable programmable read-only memory (EEPROM) to provide the intelligence.

In this article, we will introduce the ADM1041 product of Analog Devices (ADI), which integrates current detection, voltage detection, bus sharing and OrFET control, thus achieving high integration, improved flexibility and intelligence. This new device, which is also compatible with the I2C interface, can also communicate through the SMBus bus and has a built-in EEPROM. This allows great flexibility in setting the power supply and can significantly reduce the design and development time. This article introduces replacing the existing discrete solution with an integrated solution such as the ADM1041. Figure 1 shows a block diagram of a typical secondary function included in a redundant power supply.

Although power supply designers may not like to talk about cost, it is usually the main issue involved in designing a power supply. Component costs, maintenance expenses, development, testing and production all factor into the cost of the design project. The ADM1041 enables power supply designers to simplify and speed up the development of new designs. When developing an AC detection circuit, it is much faster to re-set registers than to re-solder several components. In addition, due to the high level of integration of the ADM1041, the number of components in the bill of materials (BOM) required and their cost are much lower than those of corresponding discrete solutions. This also saves inventory and ordering issues. Figure 2 shows a typical application solution for a redundant power supply secondary using the ADM1041. Other examples of cost savings will be discussed later.

End users of AC/DC power supplies increasingly want the ability to interface with the rest of the system's power supply. Discrete solutions require a microcontroller (mC), EEPROM, and lots of digital logic to perform supervisory functions. The ADM1041's SMBus interface allows it to communicate with a microprocessor or other system on the bus. This allows for greater flexibility in implementing load sharing, or advanced sharing configurations, such as thermal balancing for increased reliability. The ADM1041 includes built-in EEPROM, which stores register settings. The register contents are lockable, meaning the power supply can be deployed to the field without worrying about the end user overwriting the register values and causing a field failure. There is also a backup EEPROM on the chip that can be used to store microcontroller programming information or to store fault events when a fault occurs. The on-chip EEPROM can also operate independently. This eliminates the need for a microcontroller. Available user-friendly interface software allows design engineers to quickly program the ADM1041 without worrying about register images, referencing data sheets, or writing code. Figure 3 shows the OCP (overcurrent protection) programming window of the interface software.

When a system fails in the field or during the design phase, additional digital logic circuits are required to provide the ability to debug the system. When a fault event occurs in the power supply, the internal status register of the ADM1041 allows the user to see real-time signs to determine the cause of the fault.

The ADM1041 also provides the ability to lock the status register state, which can remember whether a fault has occurred in the past. This is useful for tracking intermittent fault conditions that occur on test benches and test sites. This additional intelligence means that more complex fault conditions can be monitored and controlled. For example, the OCP timeout is programmable, that is, the ADM1041's response to OCP events is programmable. It can be set to a constant current operating mode, or shut down the power supply when an OCP event occurs. Figure 4 shows the various monitoring flags of the ADM1041.

Product cost is critical, but it is often an afterthought for power supply designers. If a discrete component solution is used, the error caused by the sense resistor or other components is usually adjusted by the operator through a potentiometer. This manual adjustment process is quite expensive and still retains some error. The ADM1041 integrates this adjustment function on the chip. We provide a simple software algorithm for product testing, in which the operator is replaced by an analog-to-digital converter (ADC) or an automatic tester, and the software calibrates the adjustment registers of the ADM1041. This means that the operator is no longer required in the final test, thus saving production cost and time, and ensuring that each device has consistent adjustment. It can also adjust the load voltage and current sensing circuits to correct common-mode errors and differential-mode errors caused by resistor errors and amplifier errors. This is a unique advantage in high-volume applications because its production capacity is significantly improved over traditional adjustment methods. Figure 5 shows a possible production adjustment schematic.

The main design challenge today is the demand for ever-increasing power density. In server applications, power densities like 10 W/in3 are now common as end users demand smaller form factors while increasing output power. This is a very difficult dilemma because increasing output power requires larger power devices. As a result, printed circuit board (PCB) area becomes more and more precious. The ADM1041 integrates all the functions of secondary-side control in a 24-pin QSSOP package, saving valuable PCB area for increased power density. Multi-chip solutions and discrete solutions also cause layout and routing issues, as well as grounding issues. The ADM1041 can also control fans with a thermistor, as thermal management becomes increasingly important as power density increases.

Many power supply designs are custom designs where existing products are slightly modified to meet different user requirements. In the vast majority of projects, designers seek to reuse previous designs or parts of them because their characteristics have been thoroughly characterized, tested, and verified in the field. Minor changes to discrete solutions result in the use of several new components, all of which require thorough adjustment of their performance specifications. However, the ADM1041 has internal registers that can be configured to suit custom applications. This allows designers to reuse tried and tested circuits by simply resetting the registers of the ADM1041 for each new project. This saves the cost and time of design, development, and characterization. Changing the OCP limit or the power supply startup time is as simple as changing the appropriate register and sending it to the customer. We also provide software for designing feedback loops and include Bode plots for optimizing loop designs. Designers only need to enter basic parameters and specifications to enable the software to automatically design the filter. Figure 6 shows the panel of the voltage loop design software.

When power design engineers are given the technical specifications for new engineering projects, the challenges they face are obvious. They are required to reduce costs, increase power density, reduce form factor, speed up development time, increase integration, and increase functionality and intelligence. Since discrete power design methods cannot meet these requirements, a highly integrated and flexible single-chip solution is clearly needed.

Keywords：ADM1041 Reference address：ADM1041: Intelligent Integrated AC/DC Power Supply Controller

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