1-kW, 80 Plus Titanium, GaN + Silicon Digital AC-DC Power Supply Reference Design

The TIDA-010062 reference design from Texas Instruments is a digitally-controlled, compact 1-kW ac-dc power supply design for server power supply unit (PSU) and telecom rectifier applications combines the use of gallium-nitride FETs in the PFC stage with silicon MOSFETs in the LLC stage. The highly efficient design supports two main power stages, including a front-end continuous conduction mode (CCM) totem-pole bridgeless power factor correction (PFC) stage.

The PFC stage operates from an input voltage range of 100- to 265-Vac and generates a 380-Vdc bus. The second stage is made up of an isolated half bridge LLC stage, which generates a 12-V, 84-A nominal output.

The PFC stage features LMG341x GaN FET with integrated driver to provide enhanced efficiency across a wide load range and meet 80 plus titanium requirements. The design also supports a half-bridge LLC isolated dc-dc stage to achieve a +12-V dc output at 1-kW. Two control cards use C2000™ Piccolo™ microcontrollers to control both power stages.

Features

• 80 Plus Titanium efficiency, η=>95% @ 20%-100% load
• CCM GaN based totem pole bridgeless PFC stage with >99% peak efficiency, enabled by LMG341x GaN FET with integrated driver
• Half-bridge Si MOSFET LLC stage with >98% peak efficiency
• Fast load transient, Vo change within 300mV @ 2.5A/us slew rate
• Low iTHD, <10%@10% load, <5% @ 20% load, <2% @ >50% load
• Power density 41W/in³, 38-mm by 66-mm by 160-mm

The block diagram below shows the high-level block diagram of the design. In this design, two TMS320F280049 C2000™ Piccolo™ control cards are used respectively for the controller of the PFC stage and LLC stage, and an LMG3410 GaN daughter card is used for totem pole half-bridge switching.

TIDA-010062 block diagram (click on image to enlarge)

A silicon MOSFET-based synchronous rectifier, driven by the UCC27714 half-bridge driver, reduces power loss in the low-frequency half bridge at the input. Another silicon MOSFET-based synchronous rectifier used is driven by the UCC21540 isolated half-bridge driver for LLC half-bridge switching. The input current is sensed by a Hall-effect sensor TMCS1100, and the DC link voltage is processed by a variable-gain amplifier stage built using the OPA237 amplifier for better accuracy at low current levels. The output current is sensed by the INA180 current-sense amplifier.

For communication between the primary and secondary control card, Fast Serial Interface (FSI) is sensed by the four-channel digital isolator ISO7742. An onboard auxiliary power supply is implemented using the UCC28911 and provides a 12-V bias for the primary side and a 6-V bias for the secondary side. The TPS560430 is used in both the primary and secondary side for regulated Vcc in control cards and control circuits.