雕虫小技

超级稳压器噪声性能测量


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最近想用LM317 联合LM7815做一款性能型稳压器,电路如右,

LM317作为前置稳压器,与一般的二级稳压电路不同的是,它的参考地是输出电压。从而第二级的稳压器两端的电压近似不变--输出电压因为负载的变动直接耦合到前置稳压器,提高了整个电路的性能。


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先来看看业界标杆Linear的LT317的表现,

LT317 0mA loading FFT-AC coupled to AP

LT317 200mA loading FFT - 90KHz BW

LT317 200mA loading RMS Noise - 90KHz BW

电路用NS的LM317和NS的二手LM7815搭建,

Super Regulator 0mA Loading FFT

Super Regulator 200mA Loading FFT - 90KHz BW

Super Regulator 200mA Loading RMS Noise - 90KHz BW

单独用LM7815的表现,

LM7815 200mA Loading FFT

LM7815 200mA Loading RMS Noise 90KHz BW

其实,NS的LM317似乎比Linear的LT317在PSRR上稍胜一筹,

LM317(NS) 0mA Loading FFT

LM317(NS) 200mA Loading FFT

LM317(NS) 200mA Loading RMS Noise 90KHz BW

电源输入端使用的一个小功率变压器(8VA)桥式整流后1000uF电容滤波

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