Green power takes center stage

Page 4
Digital control is becoming increasingly common in distributed-power architectures. Leading manufacturers have chosen to support the PMBus as a way of managing and monitoring the performance of POL converters and their loads. The PMBus is an open protocol developed specifically for power-systems management. It is a serial bus, based on the System Management Bus (SMBus), itself a variant of the widely used I2C serial bus. The SMBus is already in use in computer servers so the addition of PMBus is a straightforward choice.

Commands and responses are sent over the PMBus between a system management unit and power controllers on plug-in boards or to the POL converters themselves. Products such as the GE Energy DLynx series offer customers the ability to use the communications protocol to optimize power conversion. As well as providing for monitoring and adjustment, the commands make possible complex designs to improve efficiency and detect faults automatically.

The PMBus makes it possible to manage power consumption dynamically by controlling the performance states of components such as microprocessors. For example, the Advanced Configuration and Power Interface (ACPI) makes it possible for external logic to prevent a processor from going into a high-speed, high-energy state or send it to sleep. Thanks to techniques such as system virtualization, these functions are now being used in datacenter servers to ensure that software workloads are processed using the minimum energy states of the various processors in the system.

The management protocols keep thermal stress – and the need for air conditioning – to a minimum by preventing hotspots from forming. Workloads on overused processors that might cause the device to operate at a high clock speed, which will force up its energy usage, can be spread evenly among other processors that are more lightly used. Processors that are not needed at any given time can be sent to sleep and the power to those modules reduced accordingly, all under the management of the PMBus. Standardization around PMBus makes it possible for suppliers to focus on improving capabilities and cost, not on reinventing the wheel.

Ericsson Power Modules provides both Advanced Bus Converter (ABC) and POL devices with PMBus communications. Recently, the company introduced 250 W to 300 W BMR457 Eight Brick series modules as well as the Quarter Brick BMR456 series offering 12 V at 400 W to 468 W. The digitally controlled DiPOL modules for POL use offer PMBus-compliant read and write functions and come in 12 A, 20 A and 40 A versions.