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Power Conversion: The Old Analog versus Digital… or Analog AND Digital?

EM News Bureau ,  Thursday, June 19, 2014, 14:44 Hrs  [IST]

Stephen-Stella-Microchip.jpgEmerging hybrid, or mixed-signal, power conversion controllers entering the marketplace are turning the ‘Analog vs. Digital’ mentality into a ‘Best of Digital Plus Best of Analog’ pragmatism. These devices aim to leverage the strengths of both analog and digital solutions, while mitigating their collective weaknesses. By combining analog and digital, it becomes feasible to incorporate the flexibility offered by digital solutions with the efficient performance, transient response, and load regulation found in analog solutions.

Ultimately, we live in an analog world. This puts so digital solutions at a disadvantage because they require information (feedback) to be digitized, typically through an analog-todigital converter, and then the digital control must be processed in a high-speed MCU (or DSP). The bandwidth of the digital control loop is directly related to the speed of the A/D conversion as well as the computational speed of the MCU/DSP. Want more bandwidth? Then higher-speed A/Ds and MCUs are required, and, unsurprisingly, are more expensive! Analog’s inherent strength is that it collects and maintains information in the analog domain, so a high-performance MCU or A/D converter is not required.

Microchip-MCP19111.jpgWhile analog power solutions offer very efficient control, it is not very flexible. Analog power— supply design engineers must evaluate the performance tradeoffs in the application and then optimize the analog design over the entire operating space, as well as the load profile. Although that technique has been sufficient for many years, market and industry trends, consumer expectations, and government regulations, are quickly outpacing the ability of analog design techniques to satisfy ever more efficiency requirements. The solution: power devices must offer more flexibility. This flexibility can then be used, among other things, to:

1. Enable multi-point power-conversion optimization, rather than optimizing across the entire power-conversion operating range

2. Perform as part of a system, meaning that it must be configurable to optimize the system’s efficiency over time, rather than just the power-conversion efficiency

3. Communicate information out to the system, enabling system optimization Digital-power conversion solutions are certainly flexible enough to address the above needs. Their design, however, is not trivial, and requires a significant investment in resources, tools and processes. Digital-control techniques are not similar to analog-control techniques, thus new resources will be needed, including digital-control design and software engineering. This investment proves to be a significant roadblock for many companies.

With these opportunities and challenges in mind, it makes sense to explore the possibilities of maintaining the power control in the analog domain. Again, this eliminates the need for additional specialized skills and resources, as well as avoiding increasing product costs stemming from the expensive MCUs and A/D converters needed for digital control.

Enter hybrid Analog AND Digital solutions, such as Microchip’s recently released MCP19111. The MCP19111 combines the performance of a peak current-mode analog controller with a small 8-bit microcontroller (See Figure 1). Its power regulation is completely in the analog domain, so there’s no need for a high-performance, high-speed microcontroller. Yet, the integrated 8-bit MCU provides a convenient interface to monitor and adjust the performance of the analog controller, enabling adjustments that have not been possible before. In addition to the flexibility that the integrated MCU adds by staying with a small, simple design it becomes feasible to be in a process that supports a high degree of integration. Figure 1 shows that the MCP19111 integrates not just the MCU with an analog controller, but also power MOSFET drivers and a mid-voltage LDO. This device is capable of operating over a very wide, 4.5-32V operating range, needs very few external components, and introduces a degree of flexibility in analog control not previously available.

 The power-conversion industry continues to move to Digital Power Conversion, due to its flexibility and customizability, and Analog Power conversion technologies will continue to offer cost-effective, high-performing power conversion solutions. The combination, whether you call it hybrid power conversion, mixed-signal power conversion, or simply Analog plus Digital power conversion—introduces a unique balance of performance, flexibility and cost that is attractive in many different kinds of applications.

Stephen Stella is Product Line Marketing Manager, Analog & Interface Products Division, Microchip Technology Inc.
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