Tutorial
Digitally-Controlled Power Supplies
Power-One’s Z-One architecture integrates a power system’s management and power conversion functions. This is said to cut overall system-level costs by 20% to 50% compared with more conventional approaches. It allows 32 POL converters to fully communicate with each other under the control of a Digital Power Manager (DPM). Each of these digital Z-Point-of-Load (Z-POL™) converters can operate with a 3 to 13 V input and provide a programmable 0.5 to 5.5Vdc output.
The Z-One system (Figure 1) uses a single-wire Z-One Digital Bus controlled by the DPM. This high-speed bi-directional bus provides both frequency synchronization and data transfer and can access all Z-POL converters in a single communication cycle. The Bus carries all the information to and from the Z-POL converters and DPM, including all operating parameters for each POL converter.
Operational parameters such as the output voltage, sequencing, tracking, monitoring, interleaving, protection thresholds are user-programmed via a Graphical User Interface (GUI) and stored in the DPM. Control of this power management system is furnished by the GUI-based Z-series Intelligent Operating System (ZIOS).
At system startup, this stored information programs the Z-POL converters. After system programming, ongoing communications between the DPM, Z-POLs, and host system support intelligent operation. You can repeat this point-and-click process for power-system optimization. The GUI only needs to be interfaced with the power system during programming and can be easily reconnected to support power system changes.
Communications with the host system uses the industry standard I2C bus communication protocol. Besides remote programming of each POL, the latest status information of each POL: output voltage, output current, and temperature are stored in the DPM and can be transmitted to the system.
Hardware for the Z-One system integrates two ASICs, the ZM7100 DPM, and the maXyz ZY7000 series of Z-POL converters. The ZM7100 DPM programs and controls sequencing, tracking, supply supervision, and intelligence with aid of A/D converters.
PMBus Defines Standard for Digital Control of Power Management Subsystems
PMBus, or Power Management Bus, is a new open standard specification that defines a digital communications protocol for controlling power conversion and management devices. It is a collaborative effort involving both power supply and semiconductor companies. Included in this effort are Artesyn Technologies, Astec/Emerson Network Power, Intersil Corporation, Microchip Technology, Texas Instruments, Volterra Semiconductor, Summit Microelectronics and Zilker Labs, Inc.
The PMBus allows power converters to be configured, monitored and maintained according to a standard set of commands. Using PMBus commands, a designer can set a power supply’s operating parameters, monitor its operation and perform corrective measures in response to faults or operational warnings. The ability to set a power supply’s output voltage allows the same hardware to provide different output voltages by merely re-programming. The ability to monitor and maintain a PMBus system enhances its reliability and availability.
Implementation of the PMBus specification requires the design of power supplies and their associated ICs to adhere to the required interface and commands. As shown in (Figure 2), the SMBus provides serial communication between the host computer or system manager and the PMBus compliant devices. A variation of the widely-used I2C bus, the industry-standard SMBus is a two-wire bus modified seve
