Industrial Automation Power Dilemma: Part 2
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Industrial Automation Power Dilemma: Part 2

Posted Date: 2024-01-25

Introduction

Synchronous switching technology is often used in systems to help eliminate interference that can occur when connecting or disconnecting capacitor banks to active distribution feeders. However, with its use, voltage spikes and irregularities arise.

This application note is Part 2 of a two-part series on high-voltage synchronous regulators in industrial automation power supply designs. Part 1 discusses industrial control architecture and power supply needs and dilemmas. In Part 2 of this series, we discuss how new power supplies can use synchronous switching technology while being able to withstand voltage spikes up to 60V and deliver up to 3.5A, which was previously impractical. These features simplify industrial automation system power supply design by improving efficiency, which reduces heat generation and power consumption, reduces component footprint, and limits the number of discrete external components.

New Synchronous Voltage Regulator

Synchronous voltage regulators seem to be the perfect answer to the power supply design challenges of industrial automation systems. These devices are highly efficient, limiting power consumption and reducing system temperatures. They require little space and reduce BOM cost.

Many synchronous regulators have operating voltage ratings up to 28V, and a few operate up to 40V. However, most of these devices are particularly sensitive to overvoltage because there is little margin between their operating voltage and voltage rating. Voltage spikes typical of mains power supply systems can quickly damage these components.

One solution is to use protective clamps to protect the synchronous regulator, limiting voltage spikes to levels below the component's rated voltage. However, these clamps add cost, space, and length to the design schedule, negating many of the benefits of using a synchronous regulator. This creates a dilemma for the industrial automation systems engineer: Can he/she benefit from the higher efficiency of a synchronous regulator and accept the additional hassle of voltage clamping? Or, does he/she choose an asynchronous regulator that can handle possible system overvoltage, but consumes more power and gets hotter?

Semiconductor suppliers have invested heavily in research and development to solve this dilemma, and some devices capable of handling input voltages as high as 60V or even 75V are now entering the market. However, the output current of these devices is limited to a few hundred milliamps, which is far less than the requirements of many devices used in industrial automation systems, especially PLCs.

But now, a new generation of high-voltage, high-output-current synchronous regulators is available. One example of these new high-performance chips is Maxim's MAX1750x series. The device integrates two MOSFETs, eliminating the need for external Schottky diodes and their associated external components.

This new family of synchronous regulator modules can handle voltages up to 60V and offer current outputs including 500mA, 1A, 2.5A and 3.5A. The company can also provide related products with outputs as low as tens of milliamperes for industrial automation system sensors using 4-20mA loops.

For example, the MAX17503 is designed to be 90% efficient and run 50% cooler than competing high-voltage asynchronous regulators. The device operates from an input voltage range of 4.5V to 60V and delivers up to 2.5A of output current. Figure 1 shows a typical application of the MAX17503 (and its sister product, the MAX17501) in an industrial automation system.


The MAX17501 and MAX17503 DC-DC converters target industrial automation systems.

In addition, the MAX17503 saves up to 50% board space and reduces component count by up to 75%. High-frequency switching from 200kHz to 2.2MHz allows the external inductor to be shrunk to save additional space.

In addition, the MAX1750x regulators feature PFM. PFM works by disabling reverse inductor current and skipping pulses at light loads. The advantage of PFM is higher efficiency at light loads because the quiescent current (IQ) drawn from the supply is lower.


MAX17503 application circuit with 500kHz switching frequency.

The high level of integration of the MAX1750x regulators not only reduces external component count and cost, but also eases design challenges. The engineer does not need to calculate the values ​​of the external capacitors and compensation resistors, nor does he need to obtain the sources for the external capacitors and compensation resistors because this work has already been done. Figure 2 shows the application circuit of this chip.

in conclusion

In Part 1 of this series, we examined industrial control architecture and the requirements for high-voltage synchronous regulators. In Part 2, we focus on new families of synchronous regulators and technologies that impact power budget issues. By solving the power dilemma of industrial automation systems, a new generation of synchronous regulators allows engineers to focus on optimizing the operation of industrial automation systems rather than struggling to deliver powerful power. For more information, refer to the MAX17503A evaluation kit for 3.3V output voltage applications and the MAX17503B evaluation kit for 5V output voltage applications.


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