Power Supply Design -an introduction

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Power Supply Design-an introduction

• Adapted from a Presentation
• By Doug Miller, SPU EE Alumnus

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Power SuppliesOverview

• Linear Regulators
• Switching DC-to-DC Converter Regulators

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Linear Regulators

• Simple, inexpensive
• Electrically quiet pure DC output
• Vout lt Vin
• Poor Efficiency
• e.g., if Vin 6V, Vout 3V, Efficiency near 50
• Can be physically large

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Switching Regulators

• Also known as DC-DC Converters or Switchmode
  Regulators
• Wide range of input voltages
• Multiple output voltages possible
• High Efficiency (often gt 90 )
• Compact
• - Complex, more expensive
• - Electrically noisy (not pure DC)

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Switching RegulatorsA few types

• Buck (step-down)
• Boost (step-up)
• Flyback (supports multiple outputs transformer
  needed)
• Buck-boost (step-up or down)
• Charge Pump (no inductor)

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Switching RegulatorsBuck Converter V Down only
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Switching RegulatorsBoost Converter V up only
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Switching RegulatorsBuck-Boost V Up or Down

• What the source power fluctuates up/down past the
  desired output voltage?
• A Buck-Boost regulator can go either way as
  needed
• More complicated, but often worth it

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Design Considerations

• Use linear regulators only if
• Energy conservation is not a concern
• Wasted power is insignificant (less than 1 Watt)
• Low noise is critical
• Switching regulators are finicky
• Use only the specified parts (by brand if
  possible)
• Read and follow app note precisely
• Make regulators isolatable with jumpers and/or
  fuses that can be removed