LTC4279、LT4293输出波形问题

使用LTC4279做PSE端48V供电,LT4293做PD端,连接后测量VPP和VPN两端电压发现如下图波形,之后一直是如此循环状态是什么原因? ,PSE原理图如下图所示 ,PD原理图如下图所示

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  • +1
    •  Analog Employees 
    on Nov 4, 2020 5:37 PM

    The PSE waveform looks familiar, but the voltage scale of 1kV does not see correct. If this is a true waveform, the timing at the PSE leads me to believe there is a DC disconnect at the PSE.

    What is the output of the PD connected to? The PD must draw a DC MPS minimum current to remain on. The LT4293 demo board sets the LED current limiting resistor to draw this minimum load; But the LED load is for demo purposes since the demo board output is open for connection to the application load. The PD schematic show a much larger resistor value who reduces the load current below the DC MPS if JP3 is not connected to anything. The PD must draw more than 10mA to remain on.

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  • +1
    •  Analog Employees 
    on Nov 4, 2020 5:37 PM

    The PSE waveform looks familiar, but the voltage scale of 1kV does not see correct. If this is a true waveform, the timing at the PSE leads me to believe there is a DC disconnect at the PSE.

    What is the output of the PD connected to? The PD must draw a DC MPS minimum current to remain on. The LT4293 demo board sets the LED current limiting resistor to draw this minimum load; But the LED load is for demo purposes since the demo board output is open for connection to the application load. The PD schematic show a much larger resistor value who reduces the load current below the DC MPS if JP3 is not connected to anything. The PD must draw more than 10mA to remain on.

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