Power Electronics

Power Architecture Tackles Power Management Complexity

With more and more applications relying on distributed power architectures, board-mounted power converters have been driven to achieve high levels of efficiency and power density. Those achievements have translated into space savings, as these converters have multiplied across the pc board to provide the many supply voltages needed. But most board-mounted power converters are not equipped to fully satisfy power-system timing requirements. So system designers often rely on a combination of external power management controllers, FETs and supervisory ICs to ensure proper sequencing and tracking of supplies, leading to complicated power-system designs that also sacrifice some performance.

Power-One has attacked these complexity and performance problems with its new power architecture, the Z-One digital intermediate bus architecture (digital IBA). A scalable, programmable architecture, digital IBA uses a single power management ASIC to control operation of up to 32 nonisolated point-of-load (POL) dc-dc converters via a single-wire digital bus.

With the new architecture, a host of external components associated with system-level power management ICs are eliminated (see figure). These components have not simply been integrated within the Power-One controller chip and POLs — they've been replaced in a way that provides greater control and flexibility, along with better power-conversion performance.

At the heart of the new architecture is the Z-Series POL, a nonisolated buck converter built around a digital pulse-width modulator. The POL has programmable power conversion and power management parameters, including complete control of both the high-side and low-side FETS. As a result, the POL's operation can be controlled directly to perform output tracking and sequencing without the need for efficiency-wasting FET switches in series with POL outputs. Furthermore, the POL allows users to set the types and thresholds of overcurrent, overvoltage and undervoltage protection on each converter.

Meanwhile, power conversion can be optimized through adjustment of POL switching frequency and configuration of the POL's feedback-compensation network. Consequently, the output voltage for each POL can be programmed without sacrificing performance. In many cases, this programmability will allow a single POL model to generate all the required supply voltages. In terms of current density on the board, the POLs deliver up to 52 A/in2. In addition, current sharing among POLs can be accomplished through the digital single-wire current share line. Users can synchronize the switching frequency of the POLs and control PWM interleaving.

The control of the POL is performed by Power-One's Z-Series Intelligent-power Operating System (ZIOS), which manages programming, initialization and monitoring of system operation. ZIOS features a graphical user interface (GUI) that enables the system designer to configure a complete power system, including power management functions and POL parameters, in a matter of minutes. Settings are stored in the ZM7100 digital power manager IC. The GUI's behavioral simulator allows designers to set parameters of the input source, output load and PCB distribution elements, and then simulate POL performance before loading POL settings into the digital power manager. The power manager can also be programmed on-the-fly through the host system's I2C interface.

The digital power manager and POLs will be available in the third quarter of this year. In sample quantities, pricing is less than $15 for the power manager and less than $20 for a 20-A POL.

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