Chip Brings Two-Phase PFC Benefits To Higher Power Systems

Dec 19, 2007 4:47 PM

The UCC28070 from Texas Instruments (TI) is a single-chip, interleaved power factor correction (PFC) controller for multi-kilowatt communications, server and industrial systems. The two-phase, average current-mode controller allows designers to simplify power design, increase system reliability and achieve a greater than 0.9 power factor rating.

The UCC28070 extends TI’s PFC offerings by providing a second device with two-phase interleaved operation. The first device, which the company unveiled in June, is the UCC28060. This device operates in the transition mode and is suitable for applications in the 75-W to 800-W range. In contrast, the UCC28070 works in the continuous conduction-mode and accommodates power levels ranging from 75 W to 1 kW and above. Target applications range from high-end communications systems to embedded white goods motor drives in refrigerators and air conditioners to HID lighting ballasts.

The UCC28070 helps designers meet the most stringent efficiency requirements for multi-kilowatt power systems. This PFC controller allows light-load phase management to enhance a system’s performance -- achieving higher efficiency over the entire load range. Phase management allows a system to turn on or off phases of the power supply, so that only the phases required to power the load are enabled.

In a 1.2-kW system, the UCC28070 can initiate an increase of up to 1.5% efficiency at a 20% load condition, allowing designers to exceed energy guidelines set forth by industry initiatives, such as The Green Grid, Climate Savers Computing Initiative and Project Big Green. .

The device helps increase system reliability by incorporating a unique 180 degree interleaving method, which reduces the amount of input and output current ripple and distributes the magnetics to improve thermal management. Average current mode interleaving allows a system to achieve between 50% and 100% reduction in ripple compared to today’s typical non-interleaved PFC architectures.

The UCC28070’s optional programmable-frequency dithering mode allows a designer to spread the switching frequency over a range to minimize the generation of EMI. The dithering feature helps reduce capacitor size, and it gives designers the ability to use a smaller, less expensive EMI filter.

Unique system control and protection features improve overall system reliability. For example, an output overvoltage protection scheme with an open-loop detection feature safeguards the system from common circuit-board failures. Each phase current is accurately balanced with independent current sensing to prevent excess component heating in the device’s dual-phase operation. In addition, the UCC28070 provides under-voltage lockout, cycle-by-cycle peak current limit, and a system over-temperature protection feature.

Now sampling with volume production scheduled for January, the UCC28070 is available in a 20-pin TSSOP package. Unit pricing in quantities of 100 units is $2.45.