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Distributed Powering: Non-Isolated Converters for Powering Low Voltage Logic A Presentation by

Distributed Powering: Non-Isolated Converters for Powering Low Voltage Logic A Presentation by Tyco Electronics Powers Systems, Inc China International Power Supply Exhibition November 2003. Outline. Background Powering Options Advantages of Non-isolated Converters Bus Converters

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Distributed Powering: Non-Isolated Converters for Powering Low Voltage Logic A Presentation by

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  1. Distributed Powering: Non-Isolated Converters for Powering Low Voltage Logic A Presentation by Tyco Electronics Powers Systems, Inc China International Power Supply Exhibition November 2003

  2. Outline • Background • Powering Options • Advantages of Non-isolated Converters • Bus Converters • Evaluation of Powering Options in a Typical Application • Application Considerations for Non-isolated & Bus Converters • Regulated vs Unregulated Bus converters • Input and Output Filtering • Models for Simulation • Sequencing

  3. Powering at the Circuit Pack Level: Background • Use of 48V distributed power has become popular over the past few decades • Typically each circuit pack uses isolated DC-to-DC power modules to provide the required voltages • Advantages of isolated modules on each circuit pack • Reduces system grounding problems (e.g., ground loops) • Standard, available modules from many vendors • Proven designs • Less problems with schedule compared to custom bulk powering • Fusing simplified • Small failure group size: important in high reliability systems

  4. Powering at the Circuit Pack Level: Background • Typical 1990 power requirements: 5V, 12V, 15V, 5 to 10% regulation • Multiple-output modules relatively easy and inexpensive to generate (extra winding, diode, filter) • Typical 2003 power requirement: 3.3V, 2.5V, 1.8V, 1.2V, 2 to 3% regulation • Multiple-output modules more difficult to design and expensive • Numerous single output modules can be expensive • This presentation will: • Compare various low-voltage powering options • Explore application of non-isolated converters

  5. QRW035A0F QW015A0F 48V 3.3V@12A Austin Lynx 2.5V 2.5V@8A Isolation barrier HW010A0G Austin Lynx 1.8V 1.8V@8A 48V HW010A0Y Austin Lynx 1.5V 1.5V@6A HW012A0M Isolation barrier Some Powering Architecture Choices 1 3.3V@12A 2 2.5V@8A Austin SuperLynx12/2.5V 1.8V@8A Qbus – 12V 12V 48V 3.3V@12A 1.5V@6A Austin Lynx 12/2.5V 2.5V@8A Isolation barrier Austin Lynx 12/1.8V 3 1.8V@8A Austin Lynx 12/1.5V 1.5V@6A

  6. Advantages of Latest Generation of Non-isolated Converters • Operation from low voltage (3-5V) or intermediate bus voltages (12V) • Cost << isolated converter cost • Module cost > discrete design cost, but not much • Size is much smaller than isolated converter @ same power (e.g., 5A in 11x20mm, 16A in 13x33mm) • Available in SIP or SMT • Board area < discrete design area • Faster transient response than isolated unit (no opto-coupler) • Efficiencies are very high (typ 95%) minimizing the impact of dual power processing • Output is programmable from 0.7V to 5.5V with 1 resistor • New sequencing option to control startup

  7. TEPS Non-Isolated Power Modules Package Higher Density SMT Austin MicroLynx Both 3.3/5V and 12V Input Products 5A 94% Austin MicroLynx SIP 5A 94% Austin Austin Lynx Austin SuperLynx SMT 10A 94% 6A 85% 16A 95% SIP Austin Lynx NH020 Austin SuperLynx 16A 95% 10A 94% 6A 86% Year 2004 2003 2002 Pre-2000

  8. Bus Converters • Bus converter: Isolated converter to provide power for non-isolated converters (e.g. 48V to 12V) • Lower cost, smaller size • Loose output regulation requirement • Narrow input Range (e.g., 43-54V) • Reduction in control circuitry • Alternate topologies

  9. Typical Application: Evaluation of Options • Four voltages required: • 3.3V @ 12A to power I/O • 2.5V @ 8A to power memory and I/O chips • 1.8V @ 8A to power one IC core voltage • 1.5V @ 6A to power another IC core voltage • Input voltage is 48V, with standard telecom range (36V to 75V) • Worst-case conditions are 1m/s of airflow (200LFM) and ambient temperature near modules of 70C

  10. QRW035A0F QW015A0F 48V 3.3V@12A Austin Lynx 2.5V 2.5V@8A Isolation barrier HW010A0G Austin Lynx 1.8V 1.8V@8A 48V HW010A0Y Austin Lynx 1.5V 1.5V@6A HW012A0M Isolation barrier Three Choices 1 4 isolated Converters 3.3V@12A 2 1 isolated 3 non-isolated 2.5V@8A Austin SuperLynx12/2.5V 1.8V@8A Qbus – 12V 12V 48V 3.3V@12A 1.5V@6A Austin Lynx 12/2.5V 2.5V@8A Isolation barrier Austin Lynx 12/1.8V 3 1.8V@8A 1 isolated Q-bus 4 non-isolated Austin Lynx 12/1.5V 1.5V@6A

  11. Powering Architecture Performance Comparison Outcome for our example 1 2 3 • With Non-isolated converter: Smaller and less expensive • With isolated converters: Lowest dissipation

  12. Comments on Evaluation of Options • Best choice depends upon system needs: weighting factors of cost, size, efficiency • Best choice may change with specific power needs • Number of outputs • Power level of each output • Use of linear regulators for lower currents • Non-Isolated Converters usually best when • Three or more powering voltages on a board • Low cost & size is important

  13. Non-Isolated Modules: SIP or SMT? • SIP • Manual insertion • Wave, manual, or robot soldering • Height constraints – 12.7mm and 10.2mm (Tyco Austin Series) • Small footprint • Orientation critical for cooling • SMT • Tape and reel: machine placed • Low profile – 8.5mm or less • Oriented either way for cooling

  14. Importance of Input Filtering • Discontinuous, high RMS input current • Modules have internal capacitance • Additional input filtering usually needed for: • Lower ripple • Prevent beat frequency problems • Need to consider ESR & RMS current ratings of internal and external capacitors, connector inductance, inductor current rating

  15. SMT Module Interconnect Inductance • Interconnect inductance for SMT module calculated using Finite Element Analysis

  16. Designing the Input Filtering • Tyco Power Systems is developing Pspice models that can be • Used to design input filtering by selecting components • Predict the amount of input voltage ripple

  17. Interactions Between Multiple Converters • Interaction between two converters with common source • Low/Beat Frequency Ripple – related to difference of two switching frequencies • Can be reduced by proper input filtering of each converter Vin LAB POWER SUPPLY Vo1 Vo2 Without Input LF With Input LF

  18. External Output Filtering • Output filtering not required for Austin series Modules • Additional filtering is sometimes used for • Extremely low noise requirements • Decoupling near load • Large and/or fast load transients • Austin series is stable over a wide range of loads/capacitance • With external capacitance, stability characteristics change – so an analysis is needed. • Must consider parasitic components (e.g., ESR, ESL) of external filter and distribution network, as well as the connection of the sense pin • Tyco Power systems provides the TASP (Transient and Stability Analysis Tool) to predict both Transient Response and Stability Margin • Models for use with TASP are available for many converters from the Tyco Web Site (http://power.tycoelectronics.com).

  19. Transient Response using TASP - Example

  20. Lynx II EZ-SEQUENCING • Need for sequencing of different supply voltages to a chip VCORE VI/O IC VI/O VCORE Return Voltage Tracking VI/O VI/O VCORE VCORE Ratiometric Cascading

  21. Sequencing Basics • Solutions in place today • Diodes between Outputs • Power switches between converter module and load • On/off pin for cascading • Problems • Power dissipation • Expense • Incompatibilities with modules from different vendors

  22. Lynx II EZ-SEQUENCING Sequencing capability added – new pin allows output voltage to be controlled externally during startup and shutdown Simultaneous Startup/Shutdown VSEQ Outputs VSEQ Outputs

  23. Summary and Conclusions • Non-isolated Converters are becoming an attractive option for newer systems with numerous low voltage needs • Tyco Electronics Power Systems has wide range of non-isolated products to meet the needs of these applications • Design expertise to help you is available with design tools, test data, application notes, evaluation board, recommended practices and both factory and Field Application Engineer support.

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