Telecom/Server AC/DC Power Supply Design and Precautions

Block diagram (SBD) of the server's AC/DC power supply and communication rectifier using TI's analog PFC and PWM controllers and high performance drivers and transceivers.

Block diagram

Design considerations

Currently, the challenge for AC/DC power supply developers is to achieve high power factor, low THD, and high efficiency, high power density or downsizing, high reliability, and low system cost under line and load conditions. Advanced power topologies such as interleaved PFC, bridgeless PFC, phase-shifted full-bridge DC/DC, LLC resonant DC/DC, and ZVS PWM DC/DC are widely used in today's designs to address these needs. Most AC/DC power supplies use dual PWM controllers, PFC controllers, and DC/DC controllers. However, there are also low-power, low-cost designs that use a single analog controller or a combination of PFC and DC/DC controllers to reduce component count and BOM cost.

TI's combined PFC/PWM controllers provide comprehensive control for any off-line power system that requires IEC1000-3-2 harmonic rejection. Significant performance and cost advantages are achieved by combining PFC and PWM stage control and drive signals into a single device. The performance of these devices is higher than that of earlier generations of combined controllers. One major PWM function is to have a programmable maximum duty cycle. For the PFC stage, the device improves the multiplier and uses a transconductance amplifier to enhance transient response.

The UCC27xxx MOSFET driver family includes a complete range of single and dual low-side MOSFET drivers from 2A to 9A sink and output. They have auxiliary, reverse, and directional types.

TI's integrated hot-swap power controllers are available for rated -48V systems. These devices offer load current slew rate control and peak amplitude limiting.

Most hot-swap controllers have a digital interface for precise programming and monitoring, as well as a good power/fault output.

Other high-performance analog components also provide important system functions and features such as sensor feedback, isolation, and communication transceivers.