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LM3429调光线性度差问题

现在工作情况如下:输入11-18V,输出38V 3.3A  调光是按照DATASHEET里面用PWM控制方法,PWM为20KHZ ,在占空比为0%-2%调节的时候灯光的亮度变化很大,与其它占空比调节的时候相差极大,不知道是什么原因

  • Hi,
    根据您的描述,LED在低电流下确实会随着电流变化亮度变化比较明显,其原因在于人眼视觉曲线确实存在于在低电流下对光线亮度变化更加敏感。为了能客观的观察电流变化,可以实际测量在0-2%范围变化内实际的电流输出变化。我们在更加严格要求的场合做了指数调光模式,就是为了避免在低电流下人眼视觉的感官效果。
    总结一下,可实际测量下这个调光范围内的电流变化。
    Sean
  • Hi
    datasheet提到: A minimum on-time must be maintained in order for PWM dimming to operate in the linear region of its transfer
    function. Because the controller is disabled during dimming, the PWM pulse must be long enough such that the
    energy intercepted from the input is greater than or equal to the energy being put into the LEDs.
    这个芯片用20kHz的调光频率是有些高的,改低一些,看能否改善。
  • 亲;PWM频率再高点试试?20k依据是啥?
    人眼识别力不超35Hz,这般频率;除高速摄影。