NCP1129 Universal AC Input, 5 V or 12 V Output, 20 Watt Power Supply
■ This design note describes a simple 20 watt, universal AC input, constant voltage power supply intended for AC adapters, industrial equipment, or white goods where isolation from the AC mains is required, and low cost, high efficiency, and low standby power are essential.
■ The featured power supply is a simple CCM flyback topology utilizing ON Semiconductor’s new NCP1129 monolithic switcher with integral 2 ohm, vertical channel MOSFET in a DIP8 package (U1). This Design Note provides the complete circuit schematic details and BOM for 5 volt, 4 amp power supply with a surge rating to 5 amps. Other output voltages from 3.3 Vdc up to 28 Vdc are easy to implement by modifying the values (or ratings) of a few of the secondary side output components and the flyback transformer’s secondary winding (T1). The simple input EMI filter (C1, L1) is adequate to pass Level B for FCC conducted EMI compliance. The NCP431 programmable zener is used as an error amplifier (U3), plus an optocoupler feedback scheme (U2) provides for excellent line and load regulation with high input-to-output safety isolation.
■ Performance characteristics for efficiency, output ripple, and internal MOSFET drain switching characteristics (Vds, Id) are shown in the figures and plots below for the 5V/4A version. Enhanced input transient protection (lightning, etc.) can be accomplished with the addition of an appropriate TVS device across the input of the diode bridge BD1. .
●Key Features:
■Universal AC input range (85 – 265 Vac).
■Input filter for conducted EMI attenuation.
■Very low standby (no load) power consumption.
■Frequency foldback under light load and/or overcurrent conditions.
■Pi-network output ripple filter.
■ Inherent over-current, over-voltage and over temperature protection.
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[ Smart Meters ][ Electric Meters ][ White Goods ] |
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Application note & Design Guide |
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Please see the document for details |
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SMA;SOT23 |
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English Chinese Chinese and English Japanese |
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April 2013 |
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Rev. 0 |
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DN05043/D |
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213 KB |
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