NCP1060, 12 Vout, 2 Watt Off-line Buck Regulator
■ This design note describes a very simple, low power, constant voltage output buck power converter intended for powering electronics for power goods, electrical meters and industrial equipment where isolation from the AC mains is not required. The switching element in the converter is ON Semiconductor’s NCP106x series of monolithic switchers. In this reference design, the NCP1060 is utilized with a 60 kHz switching frequency and a maximum output current of 250 mA.
■ This buck circuit utilizes a simple charge pump or “bootstap” type of voltage sensing and regulation scheme composed of D2, C1. This simple sensing technique eliminates the use of an optocoupler in the feedback loop. Thanks an on chip voltage reference and error amplifier no external active components are necessary for regulation. Just simple resistor divider composed of R2, R5 and R6 to bring portion of external voltage to FB pin. This helps to achieve load regulation +/-5% over the loads 100% down to 1% of maximum rated load. Below 1% the output voltage will rise to the value of the overvoltage clamping zener diode D4 across the output. For a 12 V output a typical value for zener diode will be 15 V and at no load the output will be clamped at this level.
■ The sensed voltage produced on C5 is also used to power the NCP1060 controller through D1 once converter has started. This auxiliary Vdd to run the chip improves the overall efficiency of the circuit and prevents the controller from running in DSS mode under normal load conditions.
■ Although this is low power output converter, full bridge rectifier is used, to lower input peak current. C4, L2 and C5 form a conducted EMI filter.
■ The 1.2 mH buck output inductor is available in several surface mount or through hole configurations from multiple vendor. This inductor should be designed to handle high voltage.
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Off-line Buck Regulator 、 constant voltage output buck power converter |
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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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English Chinese Chinese and English Japanese |
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October 2021 |
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Rev.2 |
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DN05080/D |
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602 KB |
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