SHARED INDUCTOR POWER CONVERTERS

Transcription

1 SHARED INDUCTOR POWER CONVERTERS For Use In Mobile Battery Charging and Backlighting Andrew Goessling

2 Power In Mobile Devices Do you: Have a smart phone? Care about its size? Care about its price? Expect to charge it from any USB port? Want to use it while it charges? Yes? Turns out you are not alone! You and others like you put difficult constraints on mobile device s power systems. The proposed converter aims to reduce the size and cost of mobile devices by combining the battery charging converter and the backlighting converter into a single shared inductor converter.

3 Typical Mobile Power Architecture Mobile devices contain several power converters 1 battery charger followed by several other converters Each with their own inductors s are one of the biggest and most expensive passive components + USB - Battery Charger Battery Backlight CPU Audio

4 Charger Utilization Battery charging circuit is idle the vast majority of the time Takes up precious space and cost Need internal charger to charge from USB Can we share an inductor with another converter during charging? Percentage Time Spent Charging 5% Standby 95%

5 Shared Introduction Vout1 Vout2 Vout3 Vout4 Simple single input multiple output shared inductor converter Switches are operated in a manner such that the current in the inductor is proportional to the sum of the output currents

6 Shared Introduction Vout1 Vout2 Vout3 Even simpler single input multiple output shared inductor converter Replace inductor with current source Vout4 Switches turn on one by one for a time proportional to their output current

7 Previous Work Single Input Multiple Output Multiple Input Multiple Output Multiple Input Single Output Multiple Input Multiple Output w/battery

8 Previous Work Single Input Multiple Output Shared Vout1 Vout2 Multiple Input Multiple Output Single Input Multiple Output TI Part: TPS65136 Koon, S., et al, Integrated Charge-Control Single- Dual- Output Step-Up/Step-Down. IEEE (2005) Multiple Input Single Output Multiple Input Multiple Output w/battery

9 Previous Work Shared 1 2 Single Input Multiple Output Vout1 Vout2 Shared Vout Multiple Input Multiple Output Multiple Input Single Output Bazinet, John. Dual-Input DC-DC With Integrated Ideal Diode Function. Patent 7,709, May Multiple Input Single Output Multiple Input Multiple Output w/battery

10 Previous Work Shared 1 2 Single Input Multiple Output Vout1 Vout2 Shared Vout1 Vout2 Multiple Input Multiple Output 1 2 Multiple Input Multiple Output Shared Vout Lam, Yat, et al. Single Multiple-Input Multiple-Output Switching And Method Of Use. Patent 7,256, Aug Multiple Input Single Output Multiple Input Multiple Output w/battery

11 Previous Work Shared 1 Vout1 Vout2 Shared 1 Vout1 2 Shared Vout1 Vout2 Single Input Multiple Output Multiple Input Multiple Output 1 2 Multiple Input Multiple Output w/battery Shared Vout Lam, Y., et al. Single- Dual-Input Dual-Output Switching for Integrated Battery Charging and Power Regulation. IEEE. (2003) Multiple Input Single Output Multiple Input Multiple Output w/battery

12 Previous Work Shared Vout1 Vout2 1 2 Shared Vout1 Vout2 Single Input Multiple Output Multiple Input Multiple Output 1 2 Shared Vout 1 Shared Vout1 Multiple Input Single Output Multiple Input Multiple Output w/battery

13 Previous Work Shared Charger Common problem in shared inductor converters: Coupling between outputs Changes in one output affect the other I Current = <Iout1> + <Iout2> <Iout1> <Iout2> 0 t

14 Previous Work Shared Charger Discontinuous Current Mode (DCM) solves this current starts at zero every time the converter switches outputs current at any one point in time is only related to a single output I Current <Iout1> 0 Output 1's Turn Output 2's Turn <Iout2> Output 1's Turn Output 2's Turn t

15 Previous Work Shared Charger Discontinuous Current Mode (DCM) solves this current starts at zero every time the converter switches outputs current at any one point in time is only related to a single output I Current <Iout1> 0 Output 1's Turn Output 2's Turn <Iout2> Output 1's Turn Output 2's Turn t

16 Proposed Combine battery charger and backlight converter Battery only concerned with slow time average charging current Insensitive to fast transients caused by the backlight Coupling Tradeoff Reduce coupling from battery to backlight Increase coupling from backlight to battery Backlight voltage spec is not as tight as others (e.g. CPU)

17 Proposed = 5V USB Vbatt = 3.4V LiPo Vout = 24V LED Backlighting Battery Charger Backlight Traditional Load Proposed Battery Charger & Backlight Vout Load

18 Operational Modes Four modes of operation Input has excess of power Regulate output voltage and battery charging current Input cannot support desired charging current Regulate input voltage to max power point (MPP), regulate output voltage, and give battery leftover energy Input cannot support output load Regulated input voltage to MPP, regulate output voltage, and use battery for portion of input Input absent Regulate output voltage, traditional boost from battery

19 Operational Modes Input has excess of power Regulate output voltage and battery charging current Vout Load

20 Operational Modes Input cannot support desired charging current Regulate input voltage to max power point (MPP), regulate output voltage, and give battery leftover energy Vout Load

21 Operational Modes Input cannot support output load Regulated input voltage to MPP, regulate output voltage, and use battery for portion of input Vout Load

22 Operational Modes Input absent Regulate output voltage, traditional boost from battery Vout Load

23 Work Items 1. Design and implement control of switches in each of four modes of operation 2. Design and implement smooth transitions between different modes of operation 3. Minimize cross-regulation between backlight output and battery charging

24 Potential Problems Very high battery charging current at the same time as very low backlight current Can t give backlight current every cycle Skip cycles that don t require current Switches are sized for battery charging current Bigger with more capacitance Degrades efficiency when not charging Use only a portion of the switches during these times

25 Performance Goals Short Term (MEng) Working operation in all four operational modes Cross-regulation minimized between backlight and battery Less than 10% Long Term (Commercial Product) Efficiency comparable to traditional topology (Pout/Pin) Within 5% Physical size of power system reduced > 225 mm 2 Cost of passive components (inductors) reduced > $0.25

26 Proposed Schedule 1.0 ID Project Name Days Start End 9-Jul 16-Jul 23-Jul 30-Jul 6-Aug 13-Aug 20-Aug 27-Aug 3-Sep 10-Sep 17-Sep 24-Sep 1-Oct 8-Oct 15-Oct 22-Oct 29-Oct 5-Nov 12-Nov 19-Nov 26-Nov 3-Dec 10-Dec Shared Jul 4-Dec 1.1 Design Phase 65 1-Jul 4-Sep Design control loop for mode Jul 11-Jul Test control loop for mode Jul 14-Jul Design control loop for mode Jul 24-Jul Test control loop for mode Jul 27-Jul Design control loop for mode Jul 6-Aug Test control loop for mode Aug 9-Aug Design control loop for mode Aug 19-Aug Test control loop for mode Aug 22-Aug Design smooth operational mode transitions Aug 1-Sep Test mode transitions 3 1-Sep 4-Sep 1.2 Iteration Phase 25 4-Sep 29-Sep Optimize Vout loop compensation 5 4-Sep 9-Sep Optimize Ibatt loop compensation 5 9-Sep 14-Sep Optimize loop compensation 5 14-Sep 19-Sep Test optimized system Sep 29-Sep 1.3 Implementation Phase Sep 4-Dec Implement control scheme in realizable schematic Sep 13-Oct Test realizable schematic 5 13-Oct 18-Oct Layout circuit in silicon Oct 4-Nov Test circuit including layout parasitics 5 4-Nov 9-Nov Design test PCB 4 9-Nov 13-Nov Test 1st silicon Nov 4-Dec

27 Recap Battery Charger Rarely Used Backlighting Load $$$

28 Recap Battery Charger Rarely Used Backlighting Load Combine Into Shared $$$ Vout Load $