Nu Horizons adds PMBus-capable, compact power supplies from N2Power

Power supplies have traditionally been controlled and protected by analogue circuitry that does well under one set of conditions (such as cold start-up), but suffers from stored charges in components that do not discharge quickly enough to respond to power line dropouts and load glitches. The XL275 breaks that mould by using a dedicated digital microcontroller to supervise the unit’s operation.

The microcontroller monitors the following power supply parameters: DC voltage on the bulk capacitor (supplied by the ac mains), output voltage, output current, auxiliary 12V output voltage, transformer temperature, ambient temperature, and fan tachometer. Unlike the conventional analogue circuitry that can provide timing accuracies in the range of +/- 10%-20%, the microcontroller can provide timing accuracies in the 1% range and does not suffer from stored charge memory. It responds to changing conditions 500 times each second with knowledge of the past, but without being slowed by its knowledge.

The microcontroller is responsible for enabling the main output whenever all of the required start-up conditions are met and shutting it down upon command, loss of input power or whenever the power supply’s longevity is threatened by excessive loads or temperatures. It always provides the host system with advanced warning of an impending shutdown so that it may perform its house-cleaning before power is lost.

To minimise acoustic noise, the microcontroller can turn a 12V fan on or off based upon the present load conditions and the amount of cooling air available. Because it’s programmable, the microcontroller code can be customised to fit the OEM’s requirements.

An optional I2C digital communications interface is also available to allow up to four XL275s to communicate over the same bus using the PMBus™ protocol. This communications interface allows routine remote control of the main outputs and the 12V fans. It can also notify the host if a fan fails (lost tachometer pulses). The host can query the microcontroller for its output voltage and current plus the ambient and transformer temperatures.

The XL275 Series incorporates the same industry-leading features as theXL125, XL160 and XL250 power supply families, such as active power factor correction for reduced input power, built in oring diodes, active inrush current protection, remote on-off, and high efficiency - up to 90% in some models. All N2Power supplies meet a full range of international agency approvals, including UL, DEMKO, CE Mark and FCC Class B.