Battery & Power Supply Battery & Power Supply ConsiderationsConsiderations

bybyProf. BitarProf. Bitar

Q1:Q1: What What Customer RequirementsCustomer Requirements often often affect the choice of power supply?affect the choice of power supply?

• Stationary or PortableStationary or Portable• Operation TimeOperation Time• Temperature Range of OperationTemperature Range of Operation• Size / Shape / Weight RequirementsSize / Shape / Weight Requirements

Q1:Q1: What What System RequirementsSystem Requirements often affect often affect the choice of power supply?the choice of power supply?

• Operating Voltage(s)Operating Voltage(s)• Voltage Tolerances (+/- 5%, Voltage Tolerances (+/- 5%,

10%, etc)10%, etc)• Current RequirementsCurrent Requirements

Example: Proximity AlarmExample: Proximity AlarmGoes off if someone is in your space!Goes off if someone is in your space!

IR Sensor& LED

Op-AmpGain / Filter

PowerTransistor

VibrationMotor

Micro-Controller

Voltage and Current Voltage and Current Requirements per ComponentRequirements per Component

Component Vcc IccSharp IS417F

IR Sensor 4.5 to 16V 3.5mA (typical)7.0mA (max)

LED 1.7 to 4.5V(depends on color) 20mA per LED (typical)

LM358 Op-Amp 3 to 32 V 0.7 to 3mA(depending on Vcc)

TI MSP430Microcontroller 1.8 to 3.6V 1.2 to 370uA

(depends on mode & clock freq.)

Vibration Motor(Jameco) 1.3 to 3.0V (typical) 50 to 100 mA

Q: Bases on these specifications, what operating voltage should we choose? Hmm…

Q: What current must be supplied?

What voltage do we operate at?What voltage do we operate at?

• Find a practical voltage that all Find a practical voltage that all components can function at.components can function at.

• Not always possible.Not always possible.• May require choosing a voltage larger than May require choosing a voltage larger than

the largest requirement and the largest requirement and REGULATING down to the smaller values.REGULATING down to the smaller values.

• May require finding different components.May require finding different components.

What current is required?

• How do you determine the amount of current that a power supply or battery needs to provide?

If batteries are required, what If batteries are required, what must be considered?must be considered?

• Voltage Range (Full Charge to Discharge)Voltage Range (Full Charge to Discharge)• Number of Cells RequiredNumber of Cells Required• Battery Life (ie. mA Hr Capacity)Battery Life (ie. mA Hr Capacity)• Rechargeable vs. Non-RechargeableRechargeable vs. Non-Rechargeable• Chemistry Chemistry (Alkaline, Zinc, Lead Acid, NiCd, NiMH, (Alkaline, Zinc, Lead Acid, NiCd, NiMH,

etc…)etc…)

• Temperature RangeTemperature Range• Size / Weight / CostSize / Weight / Cost

Battery Battery SpecificationsSpecifications

Battery CapacityBattery Capacity

Battery DischargeBattery Discharge(Under Constant Current Load)(Under Constant Current Load)

If an AC to DC power supply is If an AC to DC power supply is required, what must be considered?required, what must be considered?Input Voltage (120VAC, 60Hz …)Input Voltage (120VAC, 60Hz …)Output Voltage (No Load and Full Load) Output Voltage (No Load and Full Load) Maximum Output CurrentMaximum Output CurrentLine & Load RegulationLine & Load RegulationVoltage RippleVoltage RippleSize / Weight / CostSize / Weight / Cost