Ripple

Voltage Regulators Linear voltage regulators are actually pretty bad at removing ripple.  Ripple on the input will pass through and find its way onto the output.  How much will depend on the regulator and the load, but in geneal high load = more ripple passing through. Removing Ripple Using a RC filter and transistor or mosfet […]

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Standards For Power Supplies

  EN 61000-3-2 – Limits for Harmonic Current Emissions See which class your product needs its power supoply to comply with here. Lighting equipment – EN 61000-3-2 Class C complaince requried General equipment – EN 61000-3-2 Class A complaince requried    

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Line & Load Voltage Regulation

Line regulation Line regulation is the ability of the power supply to maintain its specified output voltage over changes in the input line voltage. It is expressed as percent of change in the output voltage relative to the change in the input line voltage. Load Regulation Load regulation is the ability of the power supply […]

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PC Power Supplies

AT Power Supply (original IBM PC XT AT standard) Connections: Ground (0V) +5 V +12 V (typically for disk drives and cooling fans) -5 V (typically for peripherals on the ISA bus) -12 V (typically for RS-232 serial port negative rail) Power Good – pin used to prevent digital circuitry operating while the power supply […]

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Reverse Polarity Protection

This trick using a P channel mosfet is a common way to provide reverse polarity protection on a power supply input.  It avoids the voltage drop problem of using a diode, with just the resistance of the mosfet to consider. Important – ensure you don't violate the mosfet max Vgs and Vds specification! Here's an example […]

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Switchmode DC-DC Converter Design Notes

The following diagrams are taken from: http://www.analog.com/library/analogdialogue/archives/41-06/ground_bounce.html Buck DCDC Converters This is bad: This is good: Boost DCDC Converters Ground Bounce Design Tips Switcher IC’s with internal mosfets tend to aim towards higher efficiency and therefore lower mosfet on resistance. ¬†However low on resistance means faster switching times, which contributes to noise and ground bounce. […]

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