Embedded Conference (Saturday May 21, Bangalore) By Ramesh Kankanala Microchip Technology Inc.

1. Optimization of Power Converters Efficiency Using Digital Technology Embedded Conference (Saturday May 21, Bangalore) By Ramesh Kankanala Microchip Technology Inc.

2. Agenda • What is power efficiency? • Factors affecting efficiency • Why is efficiency imperative? • Ways to digitally improve efficiency of power converters • Digital Power Management • Processor Power Saving Options

3. What is power efficiency? • Efficiency in power converters • The classical definition of efficiency is the ratio of power utilized by the load to the power consumed from the source, usually expressed as a percentage • In case of multiple power stages, the cumulative efficiency is the product of individual stage efficiencies • Efficiency consideration from power-converter perspective: • Power requirement from the source • Nature of power conversion • Effect on upstream systems • Overall power management

4. Factors Affecting Efficiency • Component selection • Internal resistance of active and passive components • Active component Switching losses • Topology of power converter • Switching frequency • Number of stages in the power converter • Line harmonics – voltage and current • Higher rated components • Higher rated harmonic filters • Filter design • Larger inductors and capacitors • Controller selection • Operating clock frequency • Device currents

5. Why is Efficiency Imperative?

6. Why is efficiency imperative? Density Density Density Density Density Density Density Loss Heat Battery Life Battery Life Battery Life Battery Life Battery Life Battery Life Battery Life Green Environment Harmonics Cost Cost Cost Cost Cost Cost Noise Regulations Cost

7. Why is efficiency imperative? • Lower Losses Will Lead to • Lower heat dissipation • lesser cooling requirements, like fans, heat sinks etc. • Lower acoustic noise due to lesser cooling requirements • longer battery life in battery-operated systems • Higher Power Density • Reduction in the cost of the system • Lesser space requirements • Meeting Standards and Regulatory Needs • Reduction in cost • Greener environment due to lesser harmonics • Contribution to Greener Environment

8. Heat and Power Loss Loss Heat • Loss in switching elements • Switching loss in MOSFETs • Conduction loss in MOSFETs • Diode/Rectifier losses • Loss in passive components • DCR in inductors • ESR in capacitors • Driver losses • Loss due to poor PF • Operation at higher RMS and peak current • More reactive energy returned to grid • Transmission and distribution losses

9. Higher Power Density Density • Higher level of integration • Digital filters for noise reduction • RC time constant using S/W blanking • S/W dead-time configurations • Power control and communication • S/W protections / Fault handling • S/W-based output sequencing • On-chip clock, analog comparators and amplifiers • S/W-based feedback compensation

10. Battery Life Battery Life • Low Power is required for battery-operated applications, such as • Portable and Handheld devices • Hand Drill • Electric Shaver • Mobile Phones • Toys • Handheld Medical Applications • Glucometer • Pulse Oximeter • Battery life directly depends on • Device ON/OFF state power losses • Power consumed by RTCC • Power for operating internal/external clock • Power for running Watchdog and Timers • Power for driving the display • Power for non-volatile memory operation

11. Going Green Going Green! Noise Harmonics • Harmonics Reduction • Single or Multiphase PFC • Improved Total Harmonic Distortion (THD) • Line noise cancellation by operating PWM out of phase • Ripple Reduction • Multiphase Buck • Output ripple cancellation by operating PWM out of phase • Switching noise reduction • Soft Switching • EMI Reduction

12. Ways to Improve Efficiency in Power Converters

13. Interleaving Power Stages - PFC IL1 ID1 ILoad PWM1 IIN IC PWM1 PWM2 Is1 IL1 90 -265V AC IL2 PFC output IL2 ID2 (IL1 + IL2) PWM2 Is2 t When duty cycle is = 50%

14. Interleaving Power Stages - Buck Converter 3.3V Output Drive Signals are Phase Shifted by 120° 12V Input Q1 Q2 120° 120° 120° Q1 Q3 Q4 Q3 Q5 Q5 Q6 GND

15. Load Balance Without Load Balancing Component and wiring differences cause some modules to work harder than others The heavily loaded modules get hotter and reliability drops causing failures – domino effect With Load Balancing Share the load equally between the converters Reliability improvement by ensuring equal stresses Buck Phase 1 Load Buck Phase 2 Load Equalization Routine Buck Phase 3

16. Phase Shedding • Power management : phase shedding with adaptive control • Reduction in switching losses • Reduction in reverse-recovery losses • Reduction in inductor core losses • Improves light-load efficiency • Phase angle control • Reduction in the ripple

17. Phase Angle Control • In multiphase PFC converters • Phase shedding at light loads should be accompanied by • Adaptive phase adjustment, depending on number of phases being shed • EMI filter size will be minimized

18. Resonant Conversion • Absence of switching losses for the power switches • Operation at higher frequencies • Smaller magnetic components and filter components • Low levels of EMI/EMC emissions • Smaller heat sinks, reduction in size and weight • Higher overall efficiency at a given power

19. Motor Control Applications Efficiency Improvement in Motor Control: • Center-Aligned Mode of PWM • Reduces EMI problems • Activation of PWM outputs such that centers of active periods are aligned • Sensorless Control • Eliminates mechanical feedback sensors • Velocity and position information derived from motor currents • Single-Shunt Current Sensing • Eliminates up to two shunt resistors • Derives current information from precise PWM switching

20. Improve performance, such as lamp life, color property and lumen maintenance Centralized control, advanced algorithm, precise power control Improve precision and dynamic from startup centralized real-time control loop algorithm High efficiency High frequency, variable frequency, quasi resonant Flexibility Topology, protection Insure IP protection Reduce aging and temperature drift caused by components Digital HID Ballast

21. Digital Power Management

22. Digital Power SMPS Digital Power Conversion Power control: Controlling the power flow in the converter by digitally adjusting the duty cycle, period, dead time, etc. Power management: Communicating with external peripherals, fault detection, monitoring, data logging, etc.

23. Advantages of Digital Power Management • Design reusability • Modular in design • Redundancy • On-site parameter changes • Easy maintenance • Better thermal management • Reliability • Ease in component selection

24. Power-Supply Sequencing sequential simultaneous 5.0v 5.0v V V 3.3v 3.3v T T offset ratio metric 5.0v 5.0v V V 3.3v 3.3v T T

25. Dynamic Control of Gains • Change of compensator parameters based on • Line voltage variations • Load changes • Optimal dynamic performance in the entire operating region • No hardware change • Reduces passive-component size • Improved step/transient response

26. Vo DC Vin DC Pulsating AC Gate drive Sync gate drive I Vout Load share IC Load share Ext Sync Remote ON/OFF Over temperature Load share Aux. PSU Microcontroller External communication External data communication Highest level of Integration Sync Rect. current doubler Full Wave Rectification Sync Rectification Active clamp converter PSFB Push Pull Half wave Rectification Half Bridge Full Bridge (DSC) dsPIC33FJ16GS502 Analog controller

27. No-Load Efficiency Improvement Techniques • Fan-speed control based on temperature rise, to optimize fan power consumption • Shutting down of fans in the case of multiple-fan cooling arrangement • Burst-mode PWM generation to reduce switching loss under light loads • Dropping individual converters in the multiple-converter systems, at light loads • Switching-frequency reduction at light loads

28. Non-linear control techniques • Adjustable dead time to improve efficiency • Dead-time insertion in PWM to avoid cross conduction between the upper and lower MOSFETs • Adaptive control of dead time to minimize the freewheeling diode conduction period • Industry claims about 1 to 5% gain in the efficiency, because of adaptive dead-time control

29. Processor Power Saving Options • Processor power consumption affects the overall efficiency • Various Power-Saving Options: SLEEP MODE • Ultimate in power reduction, everything disabled • Both the processor clock and the peripheral clock will be completely disabled • IDLE MODE • Processor clock will be disabled • Peripheral clock can be kept active, optionally • DOZE MODE • Best of both worlds • Processor clock can be operated at a fraction of the frequency of the peripheral clock

30. Thank You