Power Management SystemHardware Milestone: 0 Software Milestone: 0

Requirements:• Interface with the existing bicycle battery voltage (35-40V typical)• Provide stable, well-regulated power to each EBM subsystem• Automatic shutdown at low voltage level (35V)

Additional Aspirations:• Avoid wasting battery power with high efficiency design• Minimize complexity

Objectives:1. Identify all voltage/current needs from subsystems2. Identify subsystem I/O software requirements3. Develop “Power Budget” and battery charge life4. Research specific solutions and identify component candidates5. Design and model hardware schematic6. Alpha test under laboratory conditions7. Integrate into EBM subsystems and measure performance

Power Management SystemHardware Milestone: 0

Solution Method Decision Matrix

Voltage Divider Linear Regulator DC-DC Buck Converter

Efficiency Horrible (scales) Poor (~60-70%) Excellent (~90%)

Regulation Horrible Excellent Good

Part Count Excellent Excellent Horrible

Design Complexity Easy Easy Difficult

Biggest Drawback No regulation Inefficiency Switching Noise

Software Milestone: 0

• Specific power supply parts have not yet been selected pending other subsystem part selection

Power Management SystemHardware Milestone: 0 Software Milestone: 0

Requirements from top level:• Step down 35-40V main battery voltage to

first subsystem voltage level

Needs from other subsystems:• MCU

• Low voltage shutdown command

Solution being implemented: A mix of DC-DC Buck Converter and LDO Linear Regulators

Requirements from other subsystems, “Power Budget”: V_nom I_min I_nom I_max P_min P_nom P_max V mA mA mA mW mW mW

MCU (PIC) 5 - 100 - - 500 -Screen 3.3 - 17 25 - 56.1 82.5Screen Backlight 28 20 - 22 560 - 616GPS module 3.3 12 20 100 39.6 66 330Voltage Sensor - - - - - - -Current Sensor - - - - - - -Wheel Speed Sensor - - - - - - -Internal Memory - - - - - - -External Memory Module - - - - - - -