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Original question:

LM5119: When the output of LM5119 is idle, the input power consumption is too large (0.1a 48V). What is the reason for this...

LM5119: When the output of LM5119 is no load, the input power consumption is especially large, up to about 4W.What's the reason?

2018
Expert 2630 points
Part Number: LM5119

When the output of LM5119 is no load, the input power consumption is especially large, up to about 4W.What's the reason?
Should the resistance between IC VIN pin and +48V be increased?
When the input is 48V, the resistance between VIN and 48V is too small, is it the reason for the increase of power consumption?
If external power supply is used, the input power consumption of LM5119 will be reduced,
However, the IC internal power supply of LM5119 is used within a short time of starting up
If the LM5119's internal power supply is completely disabled, sometimes the switch will have no output
Is it necessary to use the internal power supply for LM5119 before switching to the external power supply after the normal operation of LM5119?
How to solve the problem of high no-load input power consumption when IC internal power supply is used?

  • 0
    Expert 2630 points
    When the output of LM5119 is no load, the input power consumption is especially large, up to about 4W.What's the reason?
    When the output of LM5119 is idle, the input power consumption is too large (0.1a 48V). What is the reason for this?
    We made the products according to the attached schematic diagram
    48 v input
    Output 8 a 42 v
    When the output is 0 load, the input power consumption is 48V, 0.1a?What's the reason?
    Should the resistance between IC VIN pin and +48V be increased?
    When the input is 48V, the resistance between VIN and 48V is too small, is it the reason for the increase of power consumption?
    If external power supply is used, the input power consumption of LM5119 will be reduced,
    However, the IC internal power supply of LM5119 is used within a short time of starting up
    If the LM5119's internal power supply is completely disabled, sometimes the switch will have no output
    Is it necessary to use the internal power supply for LM5119 before switching to the external power supply after the normal operation of LM5119?
    How to solve the problem of high no-load input power consumption when IC internal power supply is used?
  • 0 in reply to 2018
    TI__Mastermind 24075 points

    Hello, 

    First, please check if there is large switching jitter or if Vout is oscillating. If Vout is not stable, that indicates loop is not stable and the power loss could be large. 

    Second, you can pull DEMB pin (pin 17) to enable diode emulation mode to reduce power loss at no load condition. 

    Third, if you want to use external power to supply LM5119 VCC pins, make sure VCCDIS voltage below 1.25V when external power supply is not available or low. VCCDIS voltage is above 1.25V when external power supply is high or ready. Please refer to details on datasheet page 4. 

    Thanks

    Qian